Merge autoland to mozilla-central. a=merge

2019-08-28 12:39:23 +03:00 · 2019-08-28 12:39:23 +03:00 · 786d0c66bc
--- a/Cargo.lock
+++ b/Cargo.lock
@ -385,7 +385,7 @@ version = "0.1.0"
 dependencies = [
 "atomic_refcell 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 "cstr 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
- "dogear 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "dogear 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)",
 "libc 0.2.60 (registry+https://github.com/rust-lang/crates.io-index)",
 "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
 "moz_task 0.1.0",
@ -956,7 +956,7 @@ dependencies = [

 [[package]]
 name = "dogear"
-version = "0.3.1"
+version = "0.3.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
 "log 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
@ -3947,7 +3947,7 @@ dependencies = [
 "checksum devd-rs 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0d009f166c0d9e9f9909dc751630b3a6411ab7f85a153d32d01deb364ffe52a7"
 "checksum digest 0.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "05f47366984d3ad862010e22c7ce81a7dbcaebbdfb37241a620f8b6596ee135c"
 "checksum dirs 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "88972de891f6118092b643d85a0b28e0678e0f948d7f879aa32f2d5aafe97d2a"
-"checksum dogear 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "251a15c9a597d70eb53cbb0c5473d8d8c6241aef615c092030ebab27fb5b26ef"
+"checksum dogear 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "57cd6ee785daa898686f3e2fb4a2b1ce490fcd6d69665c857d16fb61b48f4aae"
 "checksum dtoa 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "09c3753c3db574d215cba4ea76018483895d7bff25a31b49ba45db21c48e50ab"
 "checksum dtoa-short 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "068d4026697c1a18f0b0bb8cfcad1b0c151b90d8edb9bf4c235ad68128920d1d"
 "checksum dwrote 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "0bd1369e02db5e9b842a9b67bce8a2fcc043beafb2ae8a799dd482d46ea1ff0d"
--- a/browser/base/content/test/siteIdentity/browser.ini
+++ b/browser/base/content/test/siteIdentity/browser.ini
@ -112,6 +112,7 @@ support-files =
  test_no_mcb_on_http_site_font2.html
  test_no_mcb_on_http_site_font2.css
 [browser_no_mcb_for_loopback.js]
+skip-if = fission # Timeouts
 tags = mcb
 support-files =
  ../general/moz.png
--- a/browser/components/aboutlogins/content/aboutLogins.css
+++ b/browser/components/aboutlogins/content/aboutLogins.css
@ -3,8 +3,9 @@
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

 body {
+  --sidebar-width: 320px;
  display: grid;
-  grid-template-columns: 320px 1fr;
+  grid-template-columns: var(--sidebar-width) 1fr;
  grid-template-rows: 75px 1fr;
  grid-template-areas: "header header"
                       "logins login";
@ -17,12 +18,13 @@ header {
  align-items: center;
  background-color: var(--in-content-box-background);
  border-bottom: 1px solid var(--in-content-box-border-color);
-  padding-inline: 60px 23px;
+  padding-inline-end: 23px;
 }

 login-filter {
-  max-width: 30%;
-  margin: auto;
+  min-width: 320px;
+  max-width: 400px;
+  margin-inline: 40px auto;
  flex-grow: 1;
  align-self: center;
 }
@ -52,8 +54,9 @@ login-item {
 }

 #branding-logo {
+  flex-basis: var(--sidebar-width);
+  flex-shrink: 0;
  height: 32px;
-  margin-inline-end: 18px;
  -moz-context-properties: fill;
  fill: #20123a;
 }
--- a/browser/components/aboutlogins/content/components/fxaccounts-button.css
+++ b/browser/components/aboutlogins/content/components/fxaccounts-button.css
@ -22,6 +22,9 @@

 .fxaccounts-avatar-button {
  cursor: pointer;
+  white-space: nowrap;
+  text-overflow: ellipsis;
+  overflow: hidden;
 }

 .fxaccount-email {
--- a/browser/components/enterprisepolicies/Policies.jsm
+++ b/browser/components/enterprisepolicies/Policies.jsm
@ -978,6 +978,12 @@ var Policies = {
    },
  },

+  OfferToSaveLoginsDefault: {
+    onBeforeUIStartup(manager, param) {
+      setDefaultPref("signon.rememberSignons", param);
+    },
+  },
+
  OverrideFirstRunPage: {
    onProfileAfterChange(manager, param) {
      let url = param ? param.href : "";
--- a/browser/components/enterprisepolicies/schemas/policies-schema.json
+++ b/browser/components/enterprisepolicies/schemas/policies-schema.json
@ -497,6 +497,10 @@
      "type": "boolean"
    },

+    "OfferToSaveLoginsDefault": {
+      "type": "boolean"
+    },
+
    "OverrideFirstRunPage": {
      "type": "URLorEmpty"
    },
--- a/browser/components/enterprisepolicies/tests/xpcshell/test_simple_pref_policies.js
+++ b/browser/components/enterprisepolicies/tests/xpcshell/test_simple_pref_policies.js
@ -456,6 +456,16 @@ const POLICIES_TESTS = [
      "browser.newtabpage.activity-stream.feeds.section.topstories": false,
    },
  },
+
+  // POLICY: OfferToSaveLoginsDefault
+  {
+    policies: {
+      OfferToSaveLoginsDefault: false,
+    },
+    unlockedPrefs: {
+      "signon.rememberSignons": false,
+    },
+  },
 ];

 add_task(async function test_policy_simple_prefs() {
--- a/browser/components/extensions/parent/ext-tabs.js
+++ b/browser/components/extensions/parent/ext-tabs.js
@ -205,7 +205,9 @@ class TabsUpdateFilterEventManager extends EventManager {
    let register = (fire, filterProps) => {
      let filter = { ...filterProps };
      if (filter.urls) {
-        filter.urls = new MatchPatternSet(filter.urls);
+        filter.urls = new MatchPatternSet(filter.urls, {
+          restrictSchemes: false,
+        });
      }
      let needsModified = true;
      if (filter.properties) {
@ -944,7 +946,9 @@ this.tabs = class extends ExtensionAPI {
          queryInfo = Object.assign({}, queryInfo);

          if (queryInfo.url !== null) {
-            queryInfo.url = new MatchPatternSet([].concat(queryInfo.url));
+            queryInfo.url = new MatchPatternSet([].concat(queryInfo.url), {
+              restrictSchemes: false,
+            });
          }
          if (queryInfo.title !== null) {
            queryInfo.title = new MatchGlob(queryInfo.title);
--- a/browser/components/extensions/test/browser/browser.ini
+++ b/browser/components/extensions/test/browser/browser.ini
@ -164,6 +164,7 @@ skip-if = (verify && debug && (os == 'mac'))
 [browser_ext_pageAction_simple.js]
 [browser_ext_pageAction_telemetry.js]
 [browser_ext_pageAction_title.js]
+skip-if = fission # Timeouts Bug 1574926
 [browser_ext_popup_api_injection.js]
 [browser_ext_popup_background.js]
 [browser_ext_popup_corners.js]
--- a/browser/components/extensions/test/browser/browser_ext_tabs_query.js
+++ b/browser/components/extensions/test/browser/browser_ext_tabs_query.js
@ -21,12 +21,8 @@ add_task(async function() {
      permissions: ["tabs"],
    },

-    background: function() {
-      browser.tabs.query(
-        {
-          lastFocusedWindow: true,
-        },
-        function(tabs) {
+    async background() {
+      let tabs = await browser.tabs.query({ lastFocusedWindow: true });
      browser.test.assertEq(tabs.length, 3, "should have three tabs");

      tabs.sort((tab1, tab2) => tab1.index - tab2.index);
@ -40,27 +36,11 @@ add_task(async function() {
      browser.test.assertFalse(tabs[0].pinned, "tab 0 unpinned");
      browser.test.assertFalse(tabs[1].pinned, "tab 1 unpinned");

-          browser.test.assertEq(
-            tabs[0].url,
-            "about:robots",
-            "tab 0 url correct"
-          );
-          browser.test.assertEq(
-            tabs[1].url,
-            "about:config",
-            "tab 1 url correct"
-          );
+      browser.test.assertEq(tabs[0].url, "about:robots", "tab 0 url correct");
+      browser.test.assertEq(tabs[1].url, "about:config", "tab 1 url correct");

-          browser.test.assertEq(
-            tabs[0].status,
-            "complete",
-            "tab 0 status correct"
-          );
-          browser.test.assertEq(
-            tabs[1].status,
-            "complete",
-            "tab 1 status correct"
-          );
+      browser.test.assertEq(tabs[0].status, "complete", "tab 0 status correct");
+      browser.test.assertEq(tabs[1].status, "complete", "tab 1 status correct");

      browser.test.assertEq(
        tabs[0].title,
@ -68,9 +48,11 @@ add_task(async function() {
        "tab 0 title correct"
      );

+      tabs = await browser.tabs.query({ url: "about:blank" });
+      browser.test.assertEq(tabs.length, 1, "about:blank query finds one tab");
+      browser.test.assertEq(tabs[0].url, "about:blank", "with the correct url");
+
      browser.test.notifyPass("tabs.query");
-        }
-      );
    },
  });

--- a/browser/components/resistfingerprinting/test/browser/browser.ini
+++ b/browser/components/resistfingerprinting/test/browser/browser.ini
@ -13,6 +13,7 @@ support-files =
 [browser_block_mozAddonManager.js]
 [browser_dynamical_window_rounding.js]
 [browser_navigator.js]
+skip-if = fission # Timeouts
 [browser_netInfo.js]
 [browser_performanceAPI.js]
 [browser_roundedWindow_dialogWindow.js]
--- a/browser/components/urlbar/tests/browser/browser.ini
+++ b/browser/components/urlbar/tests/browser/browser.ini
@ -72,6 +72,7 @@ support-files =
 skip-if = (os == 'mac' && os_version == '10.14') # bug 1554807
 [browser_locationBarExternalLoad.js]
 [browser_moz_action_link.js]
+skip-if = fission # Timeouts
 [browser_new_tab_urlbar_reset.js]
 [browser_openViewOnFocus.js]
 [browser_pasteAndGo.js]
--- a/browser/config/mozconfigs/win32/mingwclang
+++ b/browser/config/mozconfigs/win32/mingwclang
@ -41,7 +41,6 @@ ac_add_options --disable-jemalloc
 ac_add_options --enable-proxy-bypass-protection

 # These aren't supported on mingw at this time
-ac_add_options --disable-maintenance-service
 ac_add_options --disable-webrtc # Bug 1393901
 ac_add_options --disable-geckodriver # Bug 1489320

--- a/browser/config/mozconfigs/win64/mingwclang
+++ b/browser/config/mozconfigs/win64/mingwclang
@ -41,7 +41,6 @@ ac_add_options --disable-jemalloc
 ac_add_options --enable-proxy-bypass-protection

 # These aren't supported on mingw at this time
-ac_add_options --disable-maintenance-service
 ac_add_options --disable-webrtc # Bug 1393901
 ac_add_options --disable-geckodriver # Bug 1489320

--- a/browser/locales/en-US/browser/policies/policies-descriptions.ftl
+++ b/browser/locales/en-US/browser/policies/policies-descriptions.ftl
@ -115,6 +115,8 @@ policy-NoDefaultBookmarks = Disable creation of the default bookmarks bundled wi

 policy-OfferToSaveLogins = Enforce the setting to allow { -brand-short-name } to offer to remember saved logins and passwords. Both true and false values are accepted.

+policy-OfferToSaveLoginsDefault = Set the default value for allowing { -brand-short-name } to offer to remember saved logins and passwords. Both true and false values are accepted.
+
 policy-OverrideFirstRunPage = Override the first run page. Set this policy to blank if you want to disable the first run page.

 policy-OverridePostUpdatePage = Override the post-update “What’s New” page. Set this policy to blank if you want to disable the post-update page.
--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@ -274,10 +274,6 @@

 %include ../shared/identity-block/identity-block.inc.css

-#wrapper-urlbar-container[place="palette"] {
-  max-width: 20em;
-}
-
 #pageAction-urlbar-shareURL,
 #pageAction-panel-shareURL {
  list-style-image: url("chrome://browser/skin/share.svg");
--- a/browser/themes/shared/customizableui/panelUI.inc.css
+++ b/browser/themes/shared/customizableui/panelUI.inc.css
@ -1699,14 +1699,13 @@ toolbarpaletteitem[place="menu-panel"] > .subviewbutton-nav::after {
  border-bottom: 1px solid var(--panel-separator-color);
  display: flex;
  flex: 1 auto;
-  height: 40px; /* fixed item height to prevent flex sizing; height + 2*4px padding */
  padding: 4px;
 }

 .panel-header > label {
  flex: auto;
  font-weight: 600;
-  margin: 0;
+  margin: 4px 0;
  text-align: center;
 }

--- a/browser/themes/windows/browser.css
+++ b/browser/themes/windows/browser.css
@ -574,10 +574,6 @@ menuitem.bookmark-item {
 %include ../shared/autocomplete.inc.css
 %include ../shared/urlbar-autocomplete.inc.css

-.urlbarView {
-  font-size: 1.15em;
-}
-
 #PopupAutoComplete > richlistbox > richlistitem[originaltype~="datalist-first"] {
  border-top: 1px solid ThreeDShadow;
 }
--- a/build/docs/index.rst
+++ b/build/docs/index.rst
@ -32,6 +32,7 @@ Important Concepts
   sparse
   Support for projects building with GN <gn>
   telemetry
+   sccache-dist
   test_certificates

 integrated development environment (IDE)
--- a/build/docs/sccache-dist.rst
+++ b/build/docs/sccache-dist.rst
@ -0,0 +1,117 @@
+.. _sccache_dist:
+
+==================================
+Distributed sccache (sccache-dist)
+==================================
+
+`sccache <https://github.com/mozilla/sccache>`_ is a ccache-like tool written in
+rust.
+
+Distributed sccache (also referred to as sccache-dist) is being rolled out to
+Mozilla offices as a replacement for icecc. The steps for setting up your
+machine as an sccache-dist server as well as distributing your build to servers
+in your office are detailed below.
+
+In addition to improved security properties, distributed sccache offers
+distribution and caching of rust compilation, so it should be an improvement
+above and beyond what we see with icecc. Build servers run on linux and
+distributing builds is currently supported from macOS and linux machines.
+Distribution from Windows is supported in principle but hasn't seen sufficient
+testing.
+
+Steps for distributing a build as an sccache-dist client
+========================================================
+
+Start by following the instructions at https://github.com/mozilla/sccache/blob/master/docs/DistributedQuickstart.md#configure-a-client
+to configure your sccache distributed client. Ignore the note about custom
+toolchains if you're distributing compilation from linux.
+sccache 0.2.10 or above is recommended, and the auth section of your config
+must read::
+
+    [dist.auth]
+    type = "mozilla"
+
+* The scheduler url to use is: ``https://sccache1.corpdmz.<OFFICE>.mozilla.com``,
+  where <OFFICE> is, for instance, sfo1. A complete list of office short names
+  to be used can be found `here <https://docs.google.com/spreadsheets/d/1alscUTcfFyu3L0vs_S_cGi9JxF4uPrfsmwJko9annWE/edit#gid=0>`_
+
+* If you're compiling from a macOS client, there are a handful of additional
+  considerations detailed here:
+  https://github.com/mozilla/sccache/blob/master/docs/DistributedQuickstart.md#considerations-when-distributing-from-macos.
+  In particular, custom toolchains will need to be specified.
+  Run ``./mach bootstrap`` to download prebuilt toolchains and place them in
+  ``~/.mozbuild/clang-dist-toolchain.tar.xz`` and
+  ``~/.mozbuild/rustc-dist-toolchain.tar.xz``.
+
+* Add the following to your mozconfig::
+
+    ac_add_options CCACHE=/path/to/sccache
+
+* When attempting to get your client running, the output of ``sccache -s`` should
+  be consulted to confirm compilations are being distributed. To receive helpful
+  logging from the local daemon in case they aren't, run
+  ``SCCACHE_NO_DAEMON=1 RUST_LOG=sccache=trace path/to/sccache --start-server``
+  in a terminal window separate from your build prior to building.
+
+* Run ``./mach build -j<value>`` with an appropriately large ``<value>``.
+  ``sccache --dist-status`` should provide the number of cores available to you
+  (or a message if you're not connected). In the future this will be integrated
+  with the build system to automatically select an appropriate value.
+
+This should be enough to distribute your build and replace your use of icecc.
+Bear in mind there may be a few speedbumps, and please ensure your version of
+sccache is current before investigating further. Please see the common questions
+section below and ask for help if anything is preventing you from using it over
+email (dev-builds), on slack in #sccache, or in #build on irc.
+
+Steps for setting up a server
+=============================
+
+Build servers must run linux and use bubblewrap 3.0+ for sandboxing of compile
+processes. This requires a kernel 4.6 or greater, so Ubuntu 18+, RHEL 8, or
+similar.
+
+* Acquire a recent build of sccache. ``./mach bootstrap`` or
+  ``./mach artifact toolchain --from-build linux64-sccache`` will provide this.
+  ``cargo install`` may also be used, but ensure the version for the ``sccache``
+  and ``sccache-dist`` binaries you end up using is 0.2.10 or above.
+  Alternatively, the source is available at https://github.com/mozilla/sccache
+  and should be built with the ``dist-server`` feature selected if building from
+  there.
+
+* Collect the IP of your builder and request assignment of a static IP in a bug
+  filed in
+  `NetOps :: Other <https://bugzilla.mozilla.org/enter_bug.cgi?product=Infrastructure%20%26%20Operations&component=NetOps%3A%20Office%20Other>`_
+  cc sccache-admins@mozilla.com on this bug.
+
+* File a bug in
+  `Infrastructure :: Other <https://bugzilla.mozilla.org/enter_bug.cgi?product=Infrastructure+%26+Operations&component=Infrastructure%3A+Other>`_
+  asking for an sccache builder auth token to be generated for your builder.
+  The bug should include your name, office, where in the office the builder is
+  located (desk, closet, etc - so IT can physically find it if needed), the IP
+  address, and a secure method to reach you (gpg, keybase.io, etc). An auth
+  token will be generated and delivered to you.
+
+* The instructions at https://github.com/mozilla/sccache/blob/master/docs/DistributedQuickstart.md#configure-a-build-server
+  should contain everything else required to configure and run the server.
+
+
+Common questions/considerations
+===============================
+
+* My build is still slow: scache-dist can only do so much with parts of the
+  build that aren't able to be parallelized. To start debugging a slow build,
+  ensure the "Successful distributed compilations" line in the output of
+  ``sccache -s`` dominates other counts. For a full build, at least a 2-3x
+  improvement should be observed.
+
+* My build output is incomprehensible due to a flood of warnings: clang will
+  treat some warnings differently when its fed preprocessed code in a separate
+  invocation (preprocessing occurs locally with sccache-dist). See the
+  following note about disabling problematic warnings:
+  https://developer.mozilla.org/en-US/docs/Mozilla/Developer_guide/Using_Icecream#I_get_build_failures_due_to_-Werror_when_building_remotely_but_not_when_building_locally
+
+* My build fails with a message about incompatible versions of rustc between
+  dependent crates: if you're using a custom toolchain check that the version
+  of rustc in your ``rustc-dist-toolchain.tar.xz`` is the same as the version
+  you're running locally.
--- a/devtools/client/debugger/src/actions/pause/index.js
+++ b/devtools/client/debugger/src/actions/pause/index.js
@ -26,7 +26,7 @@ export { breakOnNext } from "./breakOnNext";
 export { mapFrames } from "./mapFrames";
 export { pauseOnExceptions } from "./pauseOnExceptions";
 export { selectFrame } from "./selectFrame";
-export { toggleSkipPausing } from "./skipPausing";
+export { toggleSkipPausing, setSkipPausing } from "./skipPausing";
 export { toggleMapScopes } from "./mapScopes";
 export { setExpandedScope } from "./expandScopes";
 export { generateInlinePreview } from "./inlinePreview";
--- a/devtools/client/debugger/src/actions/pause/skipPausing.js
+++ b/devtools/client/debugger/src/actions/pause/skipPausing.js
@ -18,3 +18,19 @@ export function toggleSkipPausing() {
    dispatch({ type: "TOGGLE_SKIP_PAUSING", skipPausing });
  };
 }
+
+/**
+ * @memberof actions/pause
+ * @static
+ */
+export function setSkipPausing(skipPausing: boolean) {
+  return async ({ dispatch, client, getState, sourceMaps }: ThunkArgs) => {
+    const currentlySkipping = getSkipPausing(getState());
+    if (currentlySkipping === skipPausing) {
+      return;
+    }
+
+    await client.setSkipPausing(skipPausing);
+    dispatch({ type: "TOGGLE_SKIP_PAUSING", skipPausing });
+  };
+}
--- a/devtools/client/debugger/src/actions/tests/pending-breakpoints.spec.js
+++ b/devtools/client/debugger/src/actions/tests/pending-breakpoints.spec.js
@ -30,6 +30,9 @@ jest.mock("../../utils/prefs", () => ({
    pendingBreakpoints: {},
  },
  clear: jest.fn(),
+  features: {
+    inlinePreview: true,
+  },
 }));

 import {
--- a/devtools/client/debugger/src/actions/types/UIAction.js
+++ b/devtools/client/debugger/src/actions/types/UIAction.js
@ -30,6 +30,10 @@ export type UIAction =
      +type: "TOGGLE_FRAMEWORK_GROUPING",
      +value: boolean,
    |}
+  | {|
+      +type: "TOGGLE_INLINE_PREVIEW",
+      +value: boolean,
+    |}
  | {|
      +type: "SHOW_SOURCE",
      +source: Source,
--- a/devtools/client/debugger/src/actions/ui.js
+++ b/devtools/client/debugger/src/actions/ui.js
@ -77,6 +77,15 @@ export function toggleFrameworkGrouping(toggleValue: boolean) {
  };
 }

+export function toggleInlinePreview(toggleValue: boolean) {
+  return ({ dispatch, getState }: ThunkArgs) => {
+    dispatch({
+      type: "TOGGLE_INLINE_PREVIEW",
+      value: toggleValue,
+    });
+  };
+}
+
 export function showSource(cx: Context, sourceId: string) {
  return ({ dispatch, getState }: ThunkArgs) => {
    const source = getSource(getState(), sourceId);
--- a/devtools/client/debugger/src/components/Editor/InlinePreviews.js
+++ b/devtools/client/debugger/src/components/Editor/InlinePreviews.js
@ -54,6 +54,7 @@ class InlinePreviews extends Component<Props> {
          return (
            <InlinePreviewRow
              editor={editor}
+              key={line}
              line={lineNum}
              previews={previews[line]}
              numColumnBreakpoints={numColumnBreakpoints}
--- a/devtools/client/debugger/src/components/Editor/index.js
+++ b/devtools/client/debugger/src/components/Editor/index.js
@ -37,6 +37,7 @@ import {
  getCurrentThread,
  getThreadContext,
  getSkipPausing,
+  getInlinePreview,
 } from "../../selectors";

 // Redux actions
@ -103,6 +104,7 @@ export type Props = {
  symbols: SymbolDeclarations,
  isPaused: boolean,
  skipPausing: boolean,
+  inlinePreviewEnabled: boolean,

  // Actions
  openConditionalPanel: typeof actions.openConditionalPanel,
@ -584,6 +586,7 @@ class Editor extends PureComponent<Props, State> {
      selectedSource,
      conditionalPanelLocation,
      isPaused,
+      inlinePreviewEnabled,
    } = this.props;
    const { editor, contextMenu } = this.state;

@ -611,7 +614,7 @@ class Editor extends PureComponent<Props, State> {
        {features.columnBreakpoints ? (
          <ColumnBreakpoints editor={editor} />
        ) : null}
-        {isPaused && features.inlinePreview ? (
+        {isPaused && inlinePreviewEnabled ? (
          <InlinePreviews editor={editor} selectedSource={selectedSource} />
        ) : null}
      </div>
@ -665,6 +668,7 @@ const mapStateToProps = state => {
    symbols: getSymbols(state, selectedSource),
    isPaused: getIsPaused(state, getCurrentThread(state)),
    skipPausing: getSkipPausing(state),
+    inlinePreviewEnabled: getInlinePreview(state),
  };
 };

--- a/devtools/client/debugger/src/components/Editor/menus/editor.js
+++ b/devtools/client/debugger/src/components/Editor/menus/editor.js
@ -15,6 +15,7 @@ import {
 } from "../../../utils/source";

 import { downloadFile } from "../../../utils/utils";
+import { features } from "../../../utils/prefs";

 import { isFulfilled } from "../../../utils/async-value";
 import actions from "../../../actions";
@ -159,6 +160,14 @@ const downloadFileItem = (
  click: () => downloadFile(selectedContent, getFilename(selectedSource)),
 });

+const inlinePreviewItem = (editorActions: EditorItemActions) => ({
+  id: "node-menu-inline-preview",
+  label: features.inlinePreview
+    ? L10N.getStr("inlinePreview.disable.label")
+    : L10N.getStr("inlinePreview.enable.label"),
+  click: () => editorActions.toggleInlinePreview(!features.inlinePreview),
+});
+
 export function editorMenuItems({
  cx,
  editorActions,
@ -218,6 +227,8 @@ export function editorMenuItems({
    );
  }

+  items.push({ type: "separator" }, inlinePreviewItem(editorActions));
+
  return items;
 }

@ -229,6 +240,7 @@ export type EditorItemActions = {
  jumpToMappedLocation: typeof actions.jumpToMappedLocation,
  showSource: typeof actions.showSource,
  toggleBlackBox: typeof actions.toggleBlackBox,
+  toggleInlinePreview: typeof actions.toggleInlinePreview,
 };

 export function editorItemActions(dispatch: Function) {
@ -241,6 +253,7 @@ export function editorItemActions(dispatch: Function) {
      jumpToMappedLocation: actions.jumpToMappedLocation,
      showSource: actions.showSource,
      toggleBlackBox: actions.toggleBlackBox,
+      toggleInlinePreview: actions.toggleInlinePreview,
    },
    dispatch
  );
--- a/devtools/client/debugger/src/components/SecondaryPanes/DOMMutationBreakpoints.js
+++ b/devtools/client/debugger/src/components/SecondaryPanes/DOMMutationBreakpoints.js
@ -31,6 +31,7 @@ type Props = {
  unHighlightDomElement: typeof actions.unHighlightDomElement,
  deleteBreakpoint: typeof deleteDOMMutationBreakpoint,
  toggleBreakpoint: typeof toggleDOMMutationBreakpointState,
+  setSkipPausing: typeof actions.setSkipPausing,
 };

 const localizationTerms = {
@ -40,12 +41,22 @@ const localizationTerms = {
 };

 class DOMMutationBreakpointsContents extends Component<Props> {
+  handleBreakpoint(breakpointId, shouldEnable) {
+    const { toggleBreakpoint, setSkipPausing } = this.props;
+
+    // The user has enabled a mutation breakpoint so we should no
+    // longer skip pausing
+    if (shouldEnable) {
+      setSkipPausing(false);
+    }
+    toggleBreakpoint(breakpointId, shouldEnable);
+  }
+
  renderItem(breakpoint: DOMMutationBreakpoint) {
    const {
      openElementInInspector,
      highlightDomElement,
      unHighlightDomElement,
-      toggleBreakpoint,
      deleteBreakpoint,
    } = this.props;
    const { enabled, id: breakpointId, nodeFront, mutationType } = breakpoint;
@ -55,7 +66,7 @@ class DOMMutationBreakpointsContents extends Component<Props> {
        <input
          type="checkbox"
          checked={enabled}
-          onChange={() => toggleBreakpoint(breakpointId, !enabled)}
+          onChange={() => this.handleBreakpoint(breakpointId, !enabled)}
        />
        <div className="dom-mutation-info">
          <div className="dom-mutation-label">
@ -123,6 +134,7 @@ class DomMutationBreakpoints extends Component<Props> {
        openElementInInspector={this.props.openElementInInspector}
        highlightDomElement={this.props.highlightDomElement}
        unHighlightDomElement={this.props.unHighlightDomElement}
+        setSkipPausing={this.props.setSkipPausing}
      />
    );
  }
@ -136,5 +148,6 @@ export default connect(
    openElementInInspector: actions.openElementInInspectorCommand,
    highlightDomElement: actions.highlightDomElement,
    unHighlightDomElement: actions.unHighlightDomElement,
+    setSkipPausing: actions.setSkipPausing,
  }
 )(DomMutationBreakpoints);
--- a/devtools/client/debugger/src/reducers/pause.js
+++ b/devtools/client/debugger/src/reducers/pause.js
@ -343,6 +343,20 @@ function update(
      };
    }

+    // Disable skipPausing if a breakpoint is enabled or added
+    case "SET_BREAKPOINT": {
+      return action.breakpoint.disabled
+        ? state
+        : { ...state, skipPausing: false };
+    }
+
+    case "UPDATE_EVENT_LISTENERS":
+    case "REMOVE_BREAKPOINT":
+    case "SET_XHR_BREAKPOINT":
+    case "ENABLE_XHR_BREAKPOINT": {
+      return { ...state, skipPausing: false };
+    }
+
    case "TOGGLE_SKIP_PAUSING": {
      const { skipPausing } = action;
      prefs.skipPausing = skipPausing;
--- a/devtools/client/debugger/src/reducers/ui.js
+++ b/devtools/client/debugger/src/reducers/ui.js
@ -9,7 +9,7 @@
 * @module reducers/ui
 */

-import { prefs } from "../utils/prefs";
+import { prefs, features } from "../utils/prefs";

 import type { Source, Range, SourceLocation } from "../types";

@ -37,6 +37,7 @@ export type UIState = {
  },
  conditionalPanelLocation: null | SourceLocation,
  isLogPoint: boolean,
+  inlinePreviewEnabled: boolean,
 };

 export const createUIState = (): UIState => ({
@ -51,6 +52,7 @@ export const createUIState = (): UIState => ({
  isLogPoint: false,
  orientation: "horizontal",
  viewport: null,
+  inlinePreviewEnabled: features.inlinePreview,
 });

 function update(state: UIState = createUIState(), action: Action): UIState {
@ -64,6 +66,11 @@ function update(state: UIState = createUIState(), action: Action): UIState {
      return { ...state, frameworkGroupingOn: action.value };
    }

+    case "TOGGLE_INLINE_PREVIEW": {
+      features.inlinePreview = action.value;
+      return { ...state, inlinePreviewEnabled: action.value };
+    }
+
    case "SET_ORIENTATION": {
      return { ...state, orientation: action.orientation };
    }
@ -185,4 +192,8 @@ export function getViewport(state: OuterState) {
  return state.ui.viewport;
 }

+export function getInlinePreview(state: OuterState) {
+  return state.ui.inlinePreviewEnabled;
+}
+
 export default update;
--- a/devtools/client/debugger/test/mochitest/browser_dbg-breakpoint-skipping.js
+++ b/devtools/client/debugger/test/mochitest/browser_dbg-breakpoint-skipping.js
@ -7,6 +7,19 @@ function skipPausing(dbg) {
  return waitForState(dbg, state => dbg.selectors.getSkipPausing());
 }

+function toggleBreakpoint(dbg, index) {
+  const breakpoints = findAllElements(dbg, "breakpointItems");
+  const bp = breakpoints[index];
+  const input = bp.querySelector("input");
+  input.click();
+}
+
+async function disableBreakpoint(dbg, index) {
+  const disabled = waitForDispatch(dbg, "SET_BREAKPOINT");
+  toggleBreakpoint(dbg, index);
+  await disabled;
+}
+
 /*
 * Tests toggling the skip pausing button and
 * invoking functions without pausing.
@ -25,4 +38,14 @@ add_task(async function() {
  await reload(dbg, "simple3");
  res = await invokeInTab("simple");
  is(res, 3, "simple() successfully completed");
+
+  info("Adding a breakpoint disables skipPausing");
+  await addBreakpoint(dbg, "simple3", 3);
+  await waitForState(dbg, state => !state.skipPausing);
+
+  info("Enabling a breakpoint disables skipPausing");
+  await skipPausing(dbg);
+  await disableBreakpoint(dbg, 0);
+  await toggleBreakpoint(dbg, 0);
+  await waitForState(dbg, state => !state.skipPausing);
 });
--- a/devtools/client/inspector/test/browser.ini
+++ b/devtools/client/inspector/test/browser.ini
@ -192,7 +192,7 @@ skip-if = fission && debug # Leaks windows.
 [browser_inspector_search-04.js]
 fail-if = fission
 [browser_inspector_search-05.js]
-fail-if = fission
+skip-if = fission # Timeouts
 [browser_inspector_search-06.js]
 [browser_inspector_search-07.js]
 [browser_inspector_search-08.js]
--- a/devtools/client/locales/en-US/debugger.properties
+++ b/devtools/client/locales/en-US/debugger.properties
@ -430,6 +430,14 @@ editor.jumpToMappedLocation1.accesskey=m
 downloadFile.label=Download file
 downloadFile.accesskey=d

+# LOCALIZATION NOTE (inlinePreview.enable.label): Context menu item
+# for enabling the inline preview feature
+inlinePreview.enable.label=Enable inline preview
+
+# LOCALIZATION NOTE (inlinePreview.disable.label): Context menu item
+# for disabling the inline preview feature
+inlinePreview.disable.label=Disable inline preview
+
 # LOCALIZATION NOTE (framework.disableGrouping): This is the text that appears in the
 # context menu to disable framework grouping.
 framework.disableGrouping=Disable framework grouping
--- a/devtools/client/preferences/debugger.js
+++ b/devtools/client/preferences/debugger.js
@ -83,4 +83,4 @@ pref("devtools.debugger.features.event-listeners-breakpoints", true);
 pref("devtools.debugger.features.dom-mutation-breakpoints", true);
 pref("devtools.debugger.features.log-points", true);
 pref("devtools.debugger.features.overlay-step-buttons", false);
-pref("devtools.debugger.features.inline-preview", false);
+pref("devtools.debugger.features.inline-preview", true);
--- a/devtools/client/styleeditor/test/browser.ini
+++ b/devtools/client/styleeditor/test/browser.ini
@ -79,7 +79,7 @@ support-files =
 [browser_styleeditor_autocomplete-disabled.js]
 [browser_styleeditor_bom.js]
 [browser_styleeditor_bug_740541_iframes.js]
-fail-if = fission
+skip-if = fission # Timeouts
 [browser_styleeditor_bug_851132_middle_click.js]
 [browser_styleeditor_bug_870339.js]
 [browser_styleeditor_bug_1405342_serviceworker_iframes.js]
--- a/devtools/client/webconsole/browser-console-manager.js
+++ b/devtools/client/webconsole/browser-console-manager.js
@ -18,6 +18,12 @@ loader.lazyRequireGetter(
  "BrowserConsole",
  "devtools/client/webconsole/browser-console"
 );
+loader.lazyRequireGetter(
+  this,
+  "PREFS",
+  "devtools/client/webconsole/constants",
+  true
+);

 const BC_WINDOW_FEATURES =
  "chrome,titlebar,toolbar,centerscreen,resizable,dialog=no";
@ -46,12 +52,11 @@ class BrowserConsoleManager {
   *        The target that the browser console will connect to.
   * @param nsIDOMWindow iframeWindow
   *        The window where the browser console UI is already loaded.
-   * @param Boolean fissionSupport
   * @return object
   *         A promise object for the opening of the new BrowserConsole instance.
   */
-  async openBrowserConsole(target, win, fissionSupport = false) {
-    const hud = new BrowserConsole(target, win, win, fissionSupport);
+  async openBrowserConsole(target, win) {
+    const hud = new BrowserConsole(target, win, win);
    this._browserConsole = hud;
    hud.once("destroyed", () => {
      this._browserConsole = null;
@ -73,11 +78,6 @@ class BrowserConsoleManager {
      return this._browserConsoleInitializing;
    }

-    const fissionSupport = Services.prefs.getBoolPref(
-      "devtools.browsertoolbox.fission",
-      false
-    );
-
    async function connect() {
      // The Browser console ends up using the debugger in autocomplete.
      // Because the debugger can't be running in the same compartment than its debuggee,
@ -124,6 +124,9 @@ class BrowserConsoleManager {
        win.addEventListener("DOMContentLoaded", resolve, { once: true });
      });

+      const fissionSupport = Services.prefs.getBoolPref(
+        PREFS.FEATURES.BROWSER_TOOLBOX_FISSION
+      );
      const title = fissionSupport
        ? `💥 Fission Browser Console 💥`
        : l10n.getStr("browserConsole.title");
@ -137,11 +140,7 @@ class BrowserConsoleManager {
      const target = await connect();
      await target.attach();
      const win = await openWindow(target);
-      const browserConsole = await this.openBrowserConsole(
-        target,
-        win,
-        fissionSupport
-      );
+      const browserConsole = await this.openBrowserConsole(target, win);
      return browserConsole;
    })();

--- a/devtools/client/webconsole/browser-console.js
+++ b/devtools/client/webconsole/browser-console.js
@ -35,10 +35,9 @@ class BrowserConsole extends WebConsole {
   *        The window where the browser console UI is already loaded.
   * @param nsIDOMWindow chromeWindow
   *        The window of the browser console owner.
-   * @param Boolean fissionSupport
   */
-  constructor(target, iframeWindow, chromeWindow, fissionSupport = false) {
-    super(null, iframeWindow, chromeWindow, true, fissionSupport);
+  constructor(target, iframeWindow, chromeWindow) {
+    super(null, iframeWindow, chromeWindow, true);

    this._browserConsoleTarget = target;
    this._telemetry = new Telemetry();
--- a/devtools/client/webconsole/constants.js
+++ b/devtools/client/webconsole/constants.js
@ -83,6 +83,7 @@ const prefs = {
      AUTOCOMPLETE: "devtools.webconsole.input.autocomplete",
      GROUP_WARNINGS: "devtools.webconsole.groupWarningMessages",
      EDITOR: "devtools.webconsole.features.editor",
+      BROWSER_TOOLBOX_FISSION: "devtools.browsertoolbox.fission",
    },
  },
 };
--- a/devtools/client/webconsole/test/browser/browser_webconsole_eval_in_debugger_stackframe.js
+++ b/devtools/client/webconsole/test/browser/browser_webconsole_eval_in_debugger_stackframe.js
@ -12,6 +12,10 @@ const TEST_URI =
  "test/browser/test-eval-in-stackframe.html";

 add_task(async function() {
+  // TODO: Remove this pref change when middleware for terminating requests
+  // when closing a panel is implemented
+  await pushPref("devtools.debugger.features.inline-preview", false);
+
  info("open the console");
  const hud = await openNewTabAndConsole(TEST_URI);

--- a/devtools/client/webconsole/test/browser/browser_webconsole_eval_in_debugger_stackframe2.js
+++ b/devtools/client/webconsole/test/browser/browser_webconsole_eval_in_debugger_stackframe2.js
@ -12,6 +12,10 @@ const TEST_URI =
  "test/browser/test-eval-in-stackframe.html";

 add_task(async function() {
+  // TODO: Remove this pref change when middleware for terminating requests
+  // when closing a panel is implemented
+  await pushPref("devtools.debugger.features.inline-preview", false);
+
  info("open the console");
  const hud = await openNewTabAndConsole(TEST_URI);

--- a/devtools/client/webconsole/test/browser/browser_webconsole_object_inspector_while_debugging_and_inspecting.js
+++ b/devtools/client/webconsole/test/browser/browser_webconsole_object_inspector_while_debugging_and_inspecting.js
@ -11,6 +11,10 @@ const TEST_URI =
  "test/browser/test-eval-in-stackframe.html";

 add_task(async function() {
+  // TODO: Remove this pref change when middleware for terminating requests
+  // when closing a panel is implemented
+  await pushPref("devtools.debugger.features.inline-preview", false);
+
  const hud = await openNewTabAndConsole(TEST_URI);

  info("Switch to the debugger");
--- a/devtools/client/webconsole/webconsole-connection-proxy.js
+++ b/devtools/client/webconsole/webconsole-connection-proxy.js
@ -20,13 +20,20 @@ class WebConsoleConnectionProxy {
   * @constructor
   * @param {WebConsoleUI} webConsoleUI
   *        A WebConsoleUI instance that owns this connection proxy.
-   * @param RemoteTarget target
+   * @param {RemoteTarget} target
   *        The target that the console will connect to.
+   * @param {Boolean} needContentProcessMessagesListener
+   *        Set to true to specifically add a ContentProcessMessages listener. This is
+   *        needed for non-fission Browser Console for example.
   */
-  constructor(webConsoleUI, target) {
+  constructor(
+    webConsoleUI,
+    target,
+    needContentProcessMessagesListener = false
+  ) {
    this.webConsoleUI = webConsoleUI;
    this.target = target;
-    this.fissionSupport = this.webConsoleUI.fissionSupport;
+    this.needContentProcessMessagesListener = needContentProcessMessagesListener;

    this._connecter = null;

@ -116,7 +123,7 @@ class WebConsoleConnectionProxy {
    // when we open the Browser Console or Toolbox without fission support. If Fission
    // is enabled, we don't use the ContentProcessMessages listener, but attach to the
    // content processes directly.
-    if (this.target.chrome && !this.target.isAddon && !this.fissionSupport) {
+    if (this.needContentProcessMessagesListener) {
      listeners.push("ContentProcessMessages");
    }
    return this.webConsoleClient.startListeners(listeners);
--- a/devtools/client/webconsole/webconsole-ui.js
+++ b/devtools/client/webconsole/webconsole-ui.js
@ -24,6 +24,12 @@ loader.lazyRequireGetter(
  "resource://gre/modules/AppConstants.jsm",
  true
 );
+loader.lazyRequireGetter(
+  this,
+  "PREFS",
+  "devtools/client/webconsole/constants",
+  true
+);

 const ZoomKeys = require("devtools/client/shared/zoom-keys");

@ -45,7 +51,6 @@ class WebConsoleUI {
    this.hud = hud;
    this.hudId = this.hud.hudId;
    this.isBrowserConsole = this.hud.isBrowserConsole;
-    this.fissionSupport = this.hud.fissionSupport;
    this.window = this.hud.iframeWindow;

    this._onPanelSelected = this._onPanelSelected.bind(this);
@ -257,10 +262,20 @@ class WebConsoleUI {
   *         A promise object that is resolved/reject based on the proxies connections.
   */
  async _initConnection() {
-    this.proxy = new WebConsoleConnectionProxy(this, this.hud.currentTarget);
-
    const target = this.hud.currentTarget;
-    if (this.fissionSupport && target.chrome && !target.isAddon) {
+    const fissionSupport = Services.prefs.getBoolPref(
+      PREFS.FEATURES.BROWSER_TOOLBOX_FISSION
+    );
+    const needContentProcessMessagesListener =
+      target.isParentProcess && !target.isAddon && !fissionSupport;
+
+    this.proxy = new WebConsoleConnectionProxy(
+      this,
+      target,
+      needContentProcessMessagesListener
+    );
+
+    if (fissionSupport && target.isParentProcess && !target.isAddon) {
      const { mainRoot } = target.client;
      const { processes } = await mainRoot.listProcesses();

--- a/devtools/client/webconsole/webconsole.js
+++ b/devtools/client/webconsole/webconsole.js
@ -59,20 +59,13 @@ class WebConsole {
   *        The window of the web console owner.
   * @param bool isBrowserConsole
   */
-  constructor(
-    toolbox,
-    iframeWindow,
-    chromeWindow,
-    isBrowserConsole = false,
-    fissionSupport = false
-  ) {
+  constructor(toolbox, iframeWindow, chromeWindow, isBrowserConsole = false) {
    this.toolbox = toolbox;
    this.iframeWindow = iframeWindow;
    this.chromeWindow = chromeWindow;
    this.hudId = "hud_" + ++gHudId;
    this.browserWindow = this.chromeWindow.top;
    this.isBrowserConsole = isBrowserConsole;
-    this.fissionSupport = fissionSupport;

    const element = this.browserWindow.document.documentElement;
    if (element.getAttribute("windowtype") != gDevTools.chromeWindowType) {
--- a/devtools/server/connectors/content-process-connector.js
+++ b/devtools/server/connectors/content-process-connector.js
@ -21,9 +21,6 @@ const CONTENT_PROCESS_SERVER_STARTUP_SCRIPT =
 loader.lazyRequireGetter(this, "EventEmitter", "devtools/shared/event-emitter");

 const ContentProcessConnector = {
-  // Flag to check if the content process server startup script was already loaded.
-  _contentProcessServerStartupScriptLoaded: false,
-
  /**
   * Start a DevTools server in a content process (representing the entire process, not
   * just a single frame) and add it as a child server for an active connection.
@ -36,8 +33,6 @@ const ContentProcessConnector = {
      mm.addMessageListener("debug:content-process-actor", function listener(
        msg
      ) {
-        // Arbitrarily choose the first content process to reply
-        // XXX: This code needs to be updated if we use more than one content process
        mm.removeMessageListener("debug:content-process-actor", listener);

        // Pipe Debugger message from/to parent/child via the message manager
@ -58,13 +53,15 @@ const ContentProcessConnector = {
      });

      // Load the content process server startup script only once.
-      if (!this._contentProcessServerStartupScriptLoaded) {
+      const isContentProcessServerStartupScripLoaded = Services.ppmm
+        .getDelayedProcessScripts()
+        .some(([uri]) => uri === CONTENT_PROCESS_SERVER_STARTUP_SCRIPT);
+      if (!isContentProcessServerStartupScripLoaded) {
        // Load the process script that will receive the debug:init-content-server message
        Services.ppmm.loadProcessScript(
          CONTENT_PROCESS_SERVER_STARTUP_SCRIPT,
          true
        );
-        this._contentProcessServerStartupScriptLoaded = true;
      }

      // Send a message to the content process server startup script to forward it the
--- a/devtools/server/tests/browser/browser.ini
+++ b/devtools/server/tests/browser/browser.ini
@ -144,7 +144,7 @@ skip-if = e10s # Bug 1183605 - devtools/server/tests/browser/ tests are still di
 [browser_storage_browser_toolbox_indexeddb.js]
 [browser_storage_cookies-duplicate-names.js]
 [browser_storage_dynamic_windows.js]
-fail-if = fission
+skip-if = fission # Timeouts
 [browser_storage_listings.js]
 fail-if = fission
 [browser_storage_updates.js]
--- a/dom/base/CharacterData.cpp
+++ b/dom/base/CharacterData.cpp
@ -489,6 +489,11 @@ nsresult CharacterData::BindToTree(BindContext& aContext, nsINode& aParent) {

  UpdateEditableState(false);

+  // Ensure we only do these once, in the case we move the shadow host around.
+  if (aContext.SubtreeRootChanges()) {
+    HandleShadowDOMRelatedInsertionSteps(hadParent);
+  }
+
  MOZ_ASSERT(OwnerDoc() == aParent.OwnerDoc(), "Bound to wrong document");
  MOZ_ASSERT(IsInComposedDoc() == aContext.InComposedDoc());
  MOZ_ASSERT(IsInUncomposedDoc() == aContext.InUncomposedDoc());
@ -506,6 +511,8 @@ void CharacterData::UnbindFromTree(bool aNullParent) {
  // Unset frame flags; if we need them again later, they'll get set again.
  UnsetFlags(NS_CREATE_FRAME_IF_NON_WHITESPACE | NS_REFRAME_IF_WHITESPACE);

+  HandleShadowDOMRelatedRemovalSteps(aNullParent);
+
  Document* document = GetComposedDoc();

  if (aNullParent) {
--- a/dom/base/Element.cpp
+++ b/dom/base/Element.cpp
@ -1721,6 +1721,7 @@ nsresult Element::BindToTree(BindContext& aContext, nsINode& aParent) {
    if (HasID()) {
      AddToIdTable(DoGetID());
    }
+    HandleShadowDOMRelatedInsertionSteps(hadParent);
  }

  if (MayHaveStyle() && !IsXULElement()) {
@ -1801,6 +1802,8 @@ bool WillDetachFromShadowOnUnbind(const Element& aElement, bool aNullParent) {
 }

 void Element::UnbindFromTree(bool aNullParent) {
+  HandleShadowDOMRelatedRemovalSteps(aNullParent);
+
  const bool detachingFromShadow =
      WillDetachFromShadowOnUnbind(*this, aNullParent);
  // Make sure to only remove from the ID table if our subtree root is actually
@ -1922,7 +1925,6 @@ void Element::UnbindFromTree(bool aNullParent) {

 #ifdef MOZ_XUL
  if (nsXULElement* xulElem = nsXULElement::FromNode(this)) {
-    ;
    xulElem->SetXULBindingParent(nullptr);
    clearBindingParent = false;
  }
@ -2629,7 +2631,8 @@ nsresult Element::AfterSetAttr(int32_t aNamespaceID, nsAtom* aName,
                               const nsAttrValue* aOldValue,
                               nsIPrincipal* aMaybeScriptedPrincipal,
                               bool aNotify) {
-  if (aNamespaceID == kNameSpaceID_None && aName == nsGkAtoms::part) {
+  if (aNamespaceID == kNameSpaceID_None) {
+    if (aName == nsGkAtoms::part) {
      bool isPart = !!aValue;
      if (HasPartAttribute() != isPart) {
        SetHasPartAttribute(isPart);
@ -2642,6 +2645,11 @@ nsresult Element::AfterSetAttr(int32_t aNamespaceID, nsAtom* aName,
        }
      }
      MOZ_ASSERT(HasPartAttribute() == isPart);
+    } else if (aName == nsGkAtoms::slot && GetParent()) {
+      if (ShadowRoot* shadow = GetParent()->GetShadowRoot()) {
+        shadow->MaybeReassignElement(*this);
+      }
+    }
  }
  return NS_OK;
 }
--- a/dom/base/FragmentOrElement.cpp
+++ b/dom/base/FragmentOrElement.cpp
@ -1118,7 +1118,7 @@ void nsIContent::AssertAnonymousSubtreeRelatedInvariants() const {
                   (GetParent() && GetBindingParent() == GetParent()),
               "root of native anonymous subtree must have parent equal "
               "to binding parent");
-  NS_ASSERTION(!GetParent() ||
+  NS_ASSERTION(!GetParent() || !IsInComposedDoc() ||
                   ((GetBindingParent() == GetParent()) ==
                    HasFlag(NODE_IS_ANONYMOUS_ROOT)) ||
                   // Unfortunately default content for XBL insertion points
@ -1129,7 +1129,7 @@ void nsIContent::AssertAnonymousSubtreeRelatedInvariants() const {
                   (GetBindingParent() &&
                    (GetBindingParent() == GetParent()->GetBindingParent()) ==
                        HasFlag(NODE_IS_ANONYMOUS_ROOT)),
-               "For nodes with parent, flag and GetBindingParent() check "
+               "For connected nodes, flag and GetBindingParent() check "
               "should match");
 }
 #endif
--- a/dom/base/ShadowRoot.cpp
+++ b/dom/base/ShadowRoot.cpp
@ -36,15 +36,11 @@ NS_IMPL_CYCLE_COLLECTION_TRAVERSE_BEGIN_INHERITED(ShadowRoot, DocumentFragment)
 NS_IMPL_CYCLE_COLLECTION_TRAVERSE_END

 NS_IMPL_CYCLE_COLLECTION_UNLINK_BEGIN(ShadowRoot)
-  if (tmp->GetHost()) {
-    tmp->GetHost()->RemoveMutationObserver(tmp);
-  }
  DocumentOrShadowRoot::Unlink(tmp);
 NS_IMPL_CYCLE_COLLECTION_UNLINK_END_INHERITED(DocumentFragment)

 NS_INTERFACE_MAP_BEGIN_CYCLE_COLLECTION(ShadowRoot)
  NS_INTERFACE_MAP_ENTRY_AMBIGUOUS(nsISupports, nsIContent)
-  NS_INTERFACE_MAP_ENTRY(nsIMutationObserver)
  NS_INTERFACE_MAP_ENTRY(nsIRadioGroupContainer)
 NS_INTERFACE_MAP_END_INHERITING(DocumentFragment)

@ -69,19 +65,9 @@ ShadowRoot::ShadowRoot(Element* aElement, ShadowRootMode aMode,

  ExtendedDOMSlots()->mBindingParent = aElement;
  ExtendedDOMSlots()->mContainingShadow = this;
-
-  // Add the ShadowRoot as a mutation observer on the host to watch
-  // for mutations because the insertion points in this ShadowRoot
-  // may need to be updated when the host children are modified.
-  GetHost()->AddMutationObserver(this);
 }

 ShadowRoot::~ShadowRoot() {
-  if (auto* host = GetHost()) {
-    // mHost may have been unlinked.
-    host->RemoveMutationObserver(this);
-  }
-
  if (IsInComposedDoc()) {
    OwnerDoc()->RemoveComposedDocShadowRoot(*this);
  }
@ -158,13 +144,11 @@ void ShadowRoot::Unattach() {
  MOZ_ASSERT(!HasSlots(), "Won't work!");
  if (!GetHost()) {
    // It is possible that we've been unlinked already. In such case host
-    // should have called Unbind and ShadowRoot's own unlink
-    // RemoveMutationObserver.
+    // should have called Unbind and ShadowRoot's own unlink.
    return;
  }

  Unbind();
-  GetHost()->RemoveMutationObserver(this);
  SetHost(nullptr);
 }

@ -220,8 +204,8 @@ void ShadowRoot::AddSlot(HTMLSlotElement* aSlot) {
    while (assignedNodes.Length() > 0) {
      nsINode* assignedNode = assignedNodes[0];

-      oldSlot->RemoveAssignedNode(assignedNode);
-      aSlot->AppendAssignedNode(assignedNode);
+      oldSlot->RemoveAssignedNode(*assignedNode->AsContent());
+      aSlot->AppendAssignedNode(*assignedNode->AsContent());
      doEnqueueSlotChange = true;
    }

@ -245,7 +229,7 @@ void ShadowRoot::AddSlot(HTMLSlotElement* aSlot) {
        continue;
      }
      doEnqueueSlotChange = true;
-      aSlot->AppendAssignedNode(child);
+      aSlot->AppendAssignedNode(*child);
    }

    if (doEnqueueSlotChange) {
@ -299,8 +283,8 @@ void ShadowRoot::RemoveSlot(HTMLSlotElement* aSlot) {
  while (!assignedNodes.IsEmpty()) {
    nsINode* assignedNode = assignedNodes[0];

-    aSlot->RemoveAssignedNode(assignedNode);
-    replacementSlot->AppendAssignedNode(assignedNode);
+    aSlot->RemoveAssignedNode(*assignedNode->AsContent());
+    replacementSlot->AppendAssignedNode(*assignedNode->AsContent());
  }

  aSlot->EnqueueSlotChangeEvent();
@ -488,7 +472,7 @@ void ShadowRoot::GetEventTargetParent(EventChainPreVisitor& aVisitor) {
  }
 }

-ShadowRoot::SlotAssignment ShadowRoot::SlotAssignmentFor(nsIContent* aContent) {
+ShadowRoot::SlotAssignment ShadowRoot::SlotAssignmentFor(nsIContent& aContent) {
  nsAutoString slotName;
  // Note that if slot attribute is missing, assign it to the first default
  // slot, if exists.
@ -513,7 +497,7 @@ ShadowRoot::SlotAssignment ShadowRoot::SlotAssignmentFor(nsIContent* aContent) {
    // Seek through the host's explicit children until the
    // assigned content is found.
    while (currentContent && currentContent != assignedNodes[i]) {
-      if (currentContent == aContent) {
+      if (currentContent == &aContent) {
        insertionIndex.emplace(i);
        break;
      }
@ -529,9 +513,9 @@ ShadowRoot::SlotAssignment ShadowRoot::SlotAssignmentFor(nsIContent* aContent) {
  return {slot, insertionIndex};
 }

-void ShadowRoot::MaybeReassignElement(Element* aElement) {
-  MOZ_ASSERT(aElement->GetParent() == GetHost());
-  HTMLSlotElement* oldSlot = aElement->GetAssignedSlot();
+void ShadowRoot::MaybeReassignElement(Element& aElement) {
+  MOZ_ASSERT(aElement.GetParent() == GetHost());
+  HTMLSlotElement* oldSlot = aElement.GetAssignedSlot();
  SlotAssignment assignment = SlotAssignmentFor(aElement);

  if (assignment.mSlot == oldSlot) {
@ -541,7 +525,7 @@ void ShadowRoot::MaybeReassignElement(Element* aElement) {

  if (Document* doc = GetComposedDoc()) {
    if (RefPtr<PresShell> presShell = doc->GetPresShell()) {
-      presShell->SlotAssignmentWillChange(*aElement, oldSlot, assignment.mSlot);
+      presShell->SlotAssignmentWillChange(aElement, oldSlot, assignment.mSlot);
    }
  }

@ -615,40 +599,39 @@ nsINode* ShadowRoot::CreateElementAndAppendChildAt(nsINode& aParentNode,
  return aParentNode.AppendChild(*node, rv);
 }

-void ShadowRoot::AttributeChanged(Element* aElement, int32_t aNameSpaceID,
-                                  nsAtom* aAttribute, int32_t aModType,
-                                  const nsAttrValue* aOldValue) {
-  if (aNameSpaceID != kNameSpaceID_None || aAttribute != nsGkAtoms::slot) {
+void ShadowRoot::MaybeUnslotHostChild(nsIContent& aChild) {
+  // Need to null-check the host because we may be unlinked already.
+  MOZ_ASSERT(!GetHost() || aChild.GetParent() == GetHost());
+
+  HTMLSlotElement* slot = aChild.GetAssignedSlot();
+  if (!slot) {
    return;
  }

-  if (aElement->GetParent() != GetHost()) {
-    return;
+  MOZ_DIAGNOSTIC_ASSERT(!aChild.IsRootOfAnonymousSubtree(),
+                        "How did aChild end up assigned to a slot?");
+  // If the slot is going to start showing fallback content, we need to tell
+  // layout about it.
+  if (slot->AssignedNodes().Length() == 1) {
+    InvalidateStyleAndLayoutOnSubtree(slot);
  }

-  MaybeReassignElement(aElement);
+  slot->RemoveAssignedNode(aChild);
+  slot->EnqueueSlotChangeEvent();
 }

-void ShadowRoot::ContentAppended(nsIContent* aFirstNewContent) {
-  for (nsIContent* content = aFirstNewContent; content;
-       content = content->GetNextSibling()) {
-    ContentInserted(content);
-  }
-}
-
-void ShadowRoot::ContentInserted(nsIContent* aChild) {
-  // Check to ensure that the child not an anonymous subtree root because
-  // even though its parent could be the host it may not be in the host's child
-  // list.
-  if (aChild->IsRootOfAnonymousSubtree()) {
+void ShadowRoot::MaybeSlotHostChild(nsIContent& aChild) {
+  MOZ_ASSERT(aChild.GetParent() == GetHost());
+  // Check to ensure that the child not an anonymous subtree root because even
+  // though its parent could be the host it may not be in the host's child list.
+  if (aChild.IsRootOfAnonymousSubtree()) {
    return;
  }

-  if (!aChild->IsSlotable()) {
+  if (!aChild.IsSlotable()) {
    return;
  }

-  if (aChild->GetParent() == GetHost()) {
  SlotAssignment assignment = SlotAssignmentFor(aChild);
  if (!assignment.mSlot) {
    return;
@ -665,53 +648,7 @@ void ShadowRoot::ContentInserted(nsIContent* aChild) {
    assignment.mSlot->AppendAssignedNode(aChild);
  }
  assignment.mSlot->EnqueueSlotChangeEvent();
-
  SlotStateChanged(assignment.mSlot);
-    return;
-  }
-
-  // If parent's root is a shadow root, and parent is a slot whose assigned
-  // nodes is the empty list, then run signal a slot change for parent.
-  HTMLSlotElement* slot = HTMLSlotElement::FromNodeOrNull(aChild->GetParent());
-  if (slot && slot->GetContainingShadow() == this &&
-      slot->AssignedNodes().IsEmpty()) {
-    slot->EnqueueSlotChangeEvent();
-  }
-}
-
-void ShadowRoot::ContentRemoved(nsIContent* aChild,
-                                nsIContent* aPreviousSibling) {
-  // Check to ensure that the child not an anonymous subtree root because
-  // even though its parent could be the host it may not be in the host's child
-  // list.
-  if (aChild->IsRootOfAnonymousSubtree()) {
-    return;
-  }
-
-  if (!aChild->IsSlotable()) {
-    return;
-  }
-
-  if (aChild->GetParent() == GetHost()) {
-    if (HTMLSlotElement* slot = aChild->GetAssignedSlot()) {
-      // If the slot is going to start showing fallback content, we need to tell
-      // layout about it.
-      if (slot->AssignedNodes().Length() == 1) {
-        InvalidateStyleAndLayoutOnSubtree(slot);
-      }
-      slot->RemoveAssignedNode(aChild);
-      slot->EnqueueSlotChangeEvent();
-    }
-    return;
-  }
-
-  // If parent's root is a shadow root, and parent is a slot whose assigned
-  // nodes is the empty list, then run signal a slot change for parent.
-  HTMLSlotElement* slot = HTMLSlotElement::FromNodeOrNull(aChild->GetParent());
-  if (slot && slot->GetContainingShadow() == this &&
-      slot->AssignedNodes().IsEmpty()) {
-    slot->EnqueueSlotChangeEvent();
-  }
 }

 ServoStyleRuleMap& ShadowRoot::ServoStyleRuleMap() {
--- a/dom/base/ShadowRoot.h
+++ b/dom/base/ShadowRoot.h
@ -39,7 +39,6 @@ class HTMLInputElement;

 class ShadowRoot final : public DocumentFragment,
                         public DocumentOrShadowRoot,
-                         public nsStubMutationObserver,
                         public nsIRadioGroupContainer {
 public:
  NS_IMPL_FROMNODE_HELPER(ShadowRoot, IsShadowRoot());
@ -47,16 +46,20 @@ class ShadowRoot final : public DocumentFragment,
  NS_DECL_CYCLE_COLLECTION_CLASS_INHERITED(ShadowRoot, DocumentFragment)
  NS_DECL_ISUPPORTS_INHERITED

-  NS_DECL_NSIMUTATIONOBSERVER_ATTRIBUTECHANGED
-  NS_DECL_NSIMUTATIONOBSERVER_CONTENTAPPENDED
-  NS_DECL_NSIMUTATIONOBSERVER_CONTENTINSERTED
-  NS_DECL_NSIMUTATIONOBSERVER_CONTENTREMOVED
-
  ShadowRoot(Element* aElement, ShadowRootMode aMode,
             already_AddRefed<mozilla::dom::NodeInfo>&& aNodeInfo);

  void AddSizeOfExcludingThis(nsWindowSizes&, size_t* aNodeSize) const final;

+  // Try to reassign an element to a slot.
+  void MaybeReassignElement(Element&);
+  // Called when an element is inserted as a direct child of our host. Tries to
+  // slot the child in one of our slots.
+  void MaybeSlotHostChild(nsIContent&);
+  // Called when a direct child of our host is removed. Tries to un-slot the
+  // child from the currently-assigned slot, if any.
+  void MaybeUnslotHostChild(nsIContent&);
+
  // Shadow DOM v1
  Element* Host() const {
    MOZ_ASSERT(GetHost(),
@ -106,12 +109,6 @@ class ShadowRoot final : public DocumentFragment,
    InsertSheetAt(SheetCount(), aSheet);
  }

-  /**
-   * Try to reassign an element to a slot and returns whether the assignment
-   * changed.
-   */
-  void MaybeReassignElement(Element* aElement);
-
  /**
   * Represents the insertion point in a slot for a given node.
   */
@ -131,7 +128,7 @@ class ShadowRoot final : public DocumentFragment,
   * It's the caller's responsibility to actually call InsertAssignedNode /
   * AppendAssignedNode in the slot as needed.
   */
-  SlotAssignment SlotAssignmentFor(nsIContent* aContent);
+  SlotAssignment SlotAssignmentFor(nsIContent&);

  /**
   * Explicitly invalidates the style and layout of the flattened-tree subtree
--- a/dom/base/moz.build
+++ b/dom/base/moz.build
@ -468,6 +468,12 @@ if CONFIG['INTEL_ARCHITECTURE']:
    SOURCES += ['nsTextFragmentSSE2.cpp']
    SOURCES['nsTextFragmentSSE2.cpp'].flags += CONFIG['SSE2_FLAGS']

+# Are we targeting PowerPC? If so, we can enable a SIMD version for
+# nsTextFragment.cpp as well.
+if CONFIG['CPU_ARCH'].startswith('ppc'):
+    SOURCES += ['nsTextFragmentVMX.cpp']
+    SOURCES['nsTextFragmentVMX.cpp'].flags += CONFIG['PPC_VMX_FLAGS']
+
 EXTRA_JS_MODULES += [
    'ContentAreaDropListener.jsm',
    'DOMRequestHelper.jsm',
--- a/dom/base/nsDocumentEncoder.cpp
+++ b/dom/base/nsDocumentEncoder.cpp
@ -239,7 +239,8 @@ class nsDocumentEncoder : public nsIDocumentEncoder {
  nsresult SerializeToStringRecursive(nsINode* aNode, nsAString& aStr,
                                      bool aDontSerializeRoot,
                                      uint32_t aMaxLength = 0);
-  nsresult SerializeNodeEnd(nsINode& aNode, nsAString& aStr);
+  nsresult SerializeNodeEnd(nsINode& aOriginalNode, nsAString& aStr,
+                            nsINode* aFixupNode = nullptr);
  // This serializes the content of aNode.
  nsresult SerializeToStringIterative(nsINode* aNode, nsAString& aStr);
  nsresult SerializeRangeToString(nsRange* aRange, nsAString& aOutputString);
@ -660,9 +661,8 @@ nsresult nsDocumentEncoder::SerializeNodeStart(nsINode& aOriginalNode,
        nsLayoutUtils::IsInvisibleBreak(node)) {
      return rv;
    }
-    Element* originalElement = aOriginalNode.AsElement();
-    rv = mSerializer->AppendElementStart(node->AsElement(), originalElement,
-                                         aStr);
+    rv = mSerializer->AppendElementStart(node->AsElement(),
+                                         aOriginalNode.AsElement(), aStr);
    return rv;
  }

@ -697,26 +697,33 @@ nsresult nsDocumentEncoder::SerializeNodeStart(nsINode& aOriginalNode,
  return rv;
 }

-nsresult nsDocumentEncoder::SerializeNodeEnd(nsINode& aNode, nsAString& aStr) {
+nsresult nsDocumentEncoder::SerializeNodeEnd(nsINode& aOriginalNode,
+                                             nsAString& aStr,
+                                             nsINode* aFixupNode) {
  if (mNeedsPreformatScanning) {
-    if (aNode.IsElement()) {
-      mSerializer->ForgetElementForPreformat(aNode.AsElement());
-    } else if (aNode.IsText()) {
-      const nsCOMPtr<nsINode> parent = aNode.GetParent();
+    if (aOriginalNode.IsElement()) {
+      mSerializer->ForgetElementForPreformat(aOriginalNode.AsElement());
+    } else if (aOriginalNode.IsText()) {
+      const nsCOMPtr<nsINode> parent = aOriginalNode.GetParent();
      if (parent && parent->IsElement()) {
        mSerializer->ForgetElementForPreformat(parent->AsElement());
      }
    }
  }

-  if (IsInvisibleNodeAndShouldBeSkipped(aNode)) {
+  if (IsInvisibleNodeAndShouldBeSkipped(aOriginalNode)) {
    return NS_OK;
  }

  nsresult rv = NS_OK;

-  if (aNode.IsElement()) {
-    rv = mSerializer->AppendElementEnd(aNode.AsElement(), aStr);
+  FixupNodeDeterminer fixupNodeDeterminer{mNodeFixup, aFixupNode,
+                                          aOriginalNode};
+  nsINode* node = &fixupNodeDeterminer.GetFixupNodeFallBackToOriginalNode();
+
+  if (node->IsElement()) {
+    rv = mSerializer->AppendElementEnd(node->AsElement(),
+                                       aOriginalNode.AsElement(), aStr);
  }

  return rv;
@ -773,7 +780,7 @@ nsresult nsDocumentEncoder::SerializeToStringRecursive(nsINode* aNode,
  }

  if (!aDontSerializeRoot) {
-    rv = SerializeNodeEnd(*maybeFixedNode, aStr);
+    rv = SerializeNodeEnd(*aNode, aStr, maybeFixedNode);
    NS_ENSURE_SUCCESS(rv, rv);
  }

--- a/dom/base/nsHTMLContentSerializer.cpp
+++ b/dom/base/nsHTMLContentSerializer.cpp
@ -256,7 +256,9 @@ nsHTMLContentSerializer::AppendElementStart(Element* aElement,
 }

 NS_IMETHODIMP
-nsHTMLContentSerializer::AppendElementEnd(Element* aElement, nsAString& aStr) {
+nsHTMLContentSerializer::AppendElementEnd(Element* aElement,
+                                          Element* aOriginalElement,
+                                          nsAString& aStr) {
  NS_ENSURE_ARG(aElement);

  nsAtom* name = aElement->NodeInfo()->NameAtom();
--- a/dom/base/nsHTMLContentSerializer.h
+++ b/dom/base/nsHTMLContentSerializer.h
@ -29,6 +29,7 @@ class nsHTMLContentSerializer final : public nsXHTMLContentSerializer {
                                nsAString& aStr) override;

  NS_IMETHOD AppendElementEnd(mozilla::dom::Element* aElement,
+                              mozilla::dom::Element* aOriginalElement,
                              nsAString& aStr) override;

  NS_IMETHOD AppendDocumentStart(mozilla::dom::Document* aDocument,
--- a/dom/base/nsIContent.h
+++ b/dom/base/nsIContent.h
@ -492,6 +492,22 @@ class nsIContent : public nsINode {
   */
  inline nsIContent* GetFlattenedTreeParent() const;

+ protected:
+  // Handles getting inserted or removed directly under a <slot> element.
+  // This is meant to only be called from the two functions below.
+  inline void HandleInsertionToOrRemovalFromSlot();
+
+  // Handles Shadow-DOM-related state tracking. Meant to be called near the
+  // end of BindToTree(), only if the tree we're in actually changed, that is,
+  // after the subtree has been bound to the new parent.
+  inline void HandleShadowDOMRelatedInsertionSteps(bool aHadParent);
+
+  // Handles Shadow-DOM related state tracking. Meant to be called near the
+  // beginning of UnbindFromTree(), before the node has lost the reference to
+  // its parent.
+  inline void HandleShadowDOMRelatedRemovalSteps(bool aNullParent);
+
+ public:
  /**
   * API to check if this is a link that's traversed in response to user input
   * (e.g. a click event). Specializations for HTML/SVG/generic XML allow for
--- a/dom/base/nsIContentInlines.h
+++ b/dom/base/nsIContentInlines.h
@ -221,4 +221,51 @@ inline bool nsIContent::IsInAnonymousSubtree() const {
  return !bindingParent->GetShadowRoot();
 }

+inline void nsIContent::HandleInsertionToOrRemovalFromSlot() {
+  using mozilla::dom::HTMLSlotElement;
+
+  MOZ_ASSERT(GetParentElement());
+  if (!IsInShadowTree() || IsRootOfAnonymousSubtree()) {
+    return;
+  }
+  HTMLSlotElement* slot = HTMLSlotElement::FromNode(mParent);
+  if (!slot) {
+    return;
+  }
+  // If parent's root is a shadow root, and parent is a slot whose
+  // assigned nodes is the empty list, then run signal a slot change for
+  // parent.
+  if (slot->AssignedNodes().IsEmpty()) {
+    slot->EnqueueSlotChangeEvent();
+  }
+}
+
+inline void nsIContent::HandleShadowDOMRelatedInsertionSteps(bool aHadParent) {
+  using mozilla::dom::Element;
+  using mozilla::dom::ShadowRoot;
+
+  if (!aHadParent) {
+    if (Element* parentElement = Element::FromNode(mParent)) {
+      if (ShadowRoot* shadow = parentElement->GetShadowRoot()) {
+        shadow->MaybeSlotHostChild(*this);
+      }
+      HandleInsertionToOrRemovalFromSlot();
+    }
+  }
+}
+
+inline void nsIContent::HandleShadowDOMRelatedRemovalSteps(bool aNullParent) {
+  using mozilla::dom::Element;
+  using mozilla::dom::ShadowRoot;
+
+  if (aNullParent) {
+    if (Element* parentElement = Element::FromNode(mParent)) {
+      if (ShadowRoot* shadow = parentElement->GetShadowRoot()) {
+        shadow->MaybeUnslotHostChild(*this);
+      }
+      HandleInsertionToOrRemovalFromSlot();
+    }
+  }
+}
+
 #endif  // nsIContentInlines_h
--- a/dom/base/nsIContentSerializer.h
+++ b/dom/base/nsIContentSerializer.h
@ -60,6 +60,7 @@ class nsIContentSerializer : public nsISupports {
                                nsAString& aStr) = 0;

  NS_IMETHOD AppendElementEnd(mozilla::dom::Element* aElement,
+                              mozilla::dom::Element* aOriginalElement,
                              nsAString& aStr) = 0;

  NS_IMETHOD Flush(nsAString& aStr) = 0;
--- a/dom/base/nsPlainTextSerializer.cpp
+++ b/dom/base/nsPlainTextSerializer.cpp
@ -419,7 +419,9 @@ nsPlainTextSerializer::AppendElementStart(Element* aElement,
 }

 NS_IMETHODIMP
-nsPlainTextSerializer::AppendElementEnd(Element* aElement, nsAString& aStr) {
+nsPlainTextSerializer::AppendElementEnd(Element* aElement,
+                                        Element* aOriginalElement,
+                                        nsAString& aStr) {
  NS_ENSURE_ARG(aElement);

  mElement = aElement;
--- a/dom/base/nsPlainTextSerializer.h
+++ b/dom/base/nsPlainTextSerializer.h
@ -69,6 +69,7 @@ class nsPlainTextSerializer final : public nsIContentSerializer {
                                mozilla::dom::Element* aOriginalElement,
                                nsAString& aStr) override;
  NS_IMETHOD AppendElementEnd(mozilla::dom::Element* aElement,
+                              mozilla::dom::Element* aOriginalElement,
                              nsAString& aStr) override;
  NS_IMETHOD Flush(nsAString& aStr) override;

--- a/dom/base/nsTextFragment.cpp
+++ b/dom/base/nsTextFragment.cpp
@ -19,6 +19,7 @@
 #include "mozilla/CheckedInt.h"
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/SSE.h"
+#include "mozilla/ppc.h"
 #include "nsTextFragmentImpl.h"
 #include <algorithm>

@ -166,6 +167,14 @@ int32_t FirstNon8Bit(const char16_t* str, const char16_t* end);
 }  // namespace mozilla
 #endif

+#ifdef __powerpc__
+namespace mozilla {
+namespace VMX {
+int32_t FirstNon8Bit(const char16_t* str, const char16_t* end);
+}  // namespace VMX
+}  // namespace mozilla
+#endif
+
 /*
 * This function returns -1 if all characters in str are 8 bit characters.
 * Otherwise, it returns a value less than or equal to the index of the first
@ -178,6 +187,10 @@ static inline int32_t FirstNon8Bit(const char16_t* str, const char16_t* end) {
  if (mozilla::supports_sse2()) {
    return mozilla::SSE2::FirstNon8Bit(str, end);
  }
+#elif defined(__powerpc__)
+  if (mozilla::supports_vmx()) {
+    return mozilla::VMX::FirstNon8Bit(str, end);
+  }
 #endif

  return FirstNon8BitUnvectorized(str, end);
--- a/dom/base/nsTextFragmentVMX.cpp
+++ b/dom/base/nsTextFragmentVMX.cpp
@ -0,0 +1,100 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// This file should only be compiled if you're on Power ISA.
+
+#include "nscore.h"
+#include "nsAlgorithm.h"
+#include "nsTextFragmentImpl.h"
+#include <altivec.h>
+
+namespace mozilla {
+namespace VMX {
+
+int32_t FirstNon8Bit(const char16_t* str, const char16_t* end) {
+  const uint32_t numUnicharsPerVector = 8;
+  const uint32_t numCharsPerVector = 16;
+  // Paranoia. If this assertion is wrong, change the vector loop below.
+  MOZ_ASSERT((numCharsPerVector / numUnicharsPerVector) == sizeof(char16_t));
+
+  typedef Non8BitParameters<sizeof(size_t)> p;
+  const uint32_t alignMask = p::alignMask();
+  const size_t mask = p::mask();
+  const uint32_t numUnicharsPerWord = p::numUnicharsPerWord();
+
+  const uint32_t len = end - str;
+
+  // i shall count the index in unichars; i2 shall count the index in chars.
+  uint32_t i = 0;
+  uint32_t i2 = 0;
+
+  // Align ourselves to a 16-byte boundary, as required by VMX loads.
+  uint32_t alignLen = std::min(
+      len, uint32_t(((-NS_PTR_TO_UINT32(str)) & 0xf) / sizeof(char16_t)));
+
+  if ((len - alignLen) >= numUnicharsPerVector) {
+    for (; i < alignLen; i++) {
+      if (str[i] > 255) return i;
+    }
+
+    // Construct a vector of shorts.
+#if __LITTLE_ENDIAN__
+    register const vector unsigned short gtcompare =
+        reinterpret_cast<vector unsigned short>(
+            vec_mergel(vec_splat_s8(-1), vec_splat_s8(0)));
+#else
+    register const vector unsigned short gtcompare =
+        reinterpret_cast<vector unsigned short>(
+            vec_mergel(vec_splat_s8(0), vec_splat_s8(-1)));
+#endif
+    const uint32_t vectWalkEnd =
+        ((len - i) / numUnicharsPerVector) * numUnicharsPerVector;
+    i2 = i * sizeof(char16_t);
+
+    while (1) {
+      register vector unsigned short vect;
+
+      // Check one VMX register (8 unichars) at a time. The vec_any_gt
+      // intrinsic does exactly what we want. This loop is manually unrolled;
+      // it yields notable performance improvements this way.
+#define CheckForASCII                                              \
+  vect = vec_ld(i2, reinterpret_cast<const unsigned short*>(str)); \
+  if (vec_any_gt(vect, gtcompare)) return i;                       \
+  i += numUnicharsPerVector;                                       \
+  if (!(i < vectWalkEnd)) break;                                   \
+  i2 += numCharsPerVector;
+
+      CheckForASCII CheckForASCII
+
+#undef CheckForASCII
+    }
+  } else {
+    // Align ourselves to a word boundary.
+    alignLen = std::min(len, uint32_t(((-NS_PTR_TO_UINT32(str)) & alignMask) /
+                                      sizeof(char16_t)));
+    for (; i < alignLen; i++) {
+      if (str[i] > 255) return i;
+    }
+  }
+
+  // Check one word at a time.
+  const uint32_t wordWalkEnd =
+      ((len - i) / numUnicharsPerWord) * numUnicharsPerWord;
+  for (; i < wordWalkEnd; i += numUnicharsPerWord) {
+    const size_t word = *reinterpret_cast<const size_t*>(str + i);
+    if (word & mask) return i;
+  }
+
+  // Take care of the remainder one character at a time.
+  for (; i < len; i++) {
+    if (str[i] > 255) {
+      return i;
+    }
+  }
+
+  return -1;
+}
+
+}  // namespace VMX
+}  // namespace mozilla
--- a/dom/base/nsXHTMLContentSerializer.cpp
+++ b/dom/base/nsXHTMLContentSerializer.cpp
@ -410,6 +410,7 @@ bool nsXHTMLContentSerializer::CheckElementStart(Element* aElement,
 }

 bool nsXHTMLContentSerializer::CheckElementEnd(Element* aElement,
+                                               Element* aOriginalElement,
                                               bool& aForceFormat,
                                               nsAString& aStr) {
  NS_ASSERTION(!mIsHTMLSerializer,
@ -428,7 +429,8 @@ bool nsXHTMLContentSerializer::CheckElementEnd(Element* aElement,
  }

  bool dummyFormat;
-  return nsXMLContentSerializer::CheckElementEnd(aElement, dummyFormat, aStr);
+  return nsXMLContentSerializer::CheckElementEnd(aElement, aOriginalElement,
+                                                 dummyFormat, aStr);
 }

 bool nsXHTMLContentSerializer::AppendAndTranslateEntities(
--- a/dom/base/nsXHTMLContentSerializer.h
+++ b/dom/base/nsXHTMLContentSerializer.h
@ -52,6 +52,7 @@ class nsXHTMLContentSerializer : public nsXMLContentSerializer {
                                 nsAString& aStr) override;

  virtual bool CheckElementEnd(mozilla::dom::Element* aContent,
+                               mozilla::dom::Element* aOriginalElement,
                               bool& aForceFormat, nsAString& aStr) override;

  virtual void AfterElementEnd(nsIContent* aContent, nsAString& aStr) override;
--- a/dom/base/nsXMLContentSerializer.cpp
+++ b/dom/base/nsXMLContentSerializer.cpp
@ -955,13 +955,16 @@ bool nsXMLContentSerializer::AppendEndOfElementStart(Element* aElement,
 }

 NS_IMETHODIMP
-nsXMLContentSerializer::AppendElementEnd(Element* aElement, nsAString& aStr) {
+nsXMLContentSerializer::AppendElementEnd(Element* aElement,
+                                         Element* aOriginalElement,
+                                         nsAString& aStr) {
  NS_ENSURE_ARG(aElement);

  nsIContent* content = aElement;

  bool forceFormat = false, outputElementEnd;
-  outputElementEnd = CheckElementEnd(aElement, forceFormat, aStr);
+  outputElementEnd =
+      CheckElementEnd(aElement, aOriginalElement, forceFormat, aStr);

  nsAtom* name = content->NodeInfo()->NameAtom();

@ -1083,15 +1086,12 @@ bool nsXMLContentSerializer::CheckElementStart(Element*, bool& aForceFormat,
 }

 bool nsXMLContentSerializer::CheckElementEnd(Element* aElement,
+                                             Element* aOriginalElement,
                                             bool& aForceFormat,
                                             nsAString& aStr) {
  // We don't output a separate end tag for empty element
  aForceFormat = false;
-
-  // XXXbz this is a bit messed up, but by now we don't have our fixed-up
-  // version of aElement anymore.  Let's hope fixup never changes the localName
-  // or namespace...
-  return ElementNeedsSeparateEndTag(aElement, aElement);
+  return ElementNeedsSeparateEndTag(aElement, aOriginalElement);
 }

 bool nsXMLContentSerializer::AppendToString(const char16_t aChar,
--- a/dom/base/nsXMLContentSerializer.h
+++ b/dom/base/nsXMLContentSerializer.h
@ -63,6 +63,7 @@ class nsXMLContentSerializer : public nsIContentSerializer {
                                nsAString& aStr) override;

  NS_IMETHOD AppendElementEnd(mozilla::dom::Element* aElement,
+                              mozilla::dom::Element* aOriginalElement,
                              nsAString& aStr) override;

  NS_IMETHOD Flush(nsAString& aStr) override { return NS_OK; }
@ -305,6 +306,7 @@ class nsXMLContentSerializer : public nsIContentSerializer {
   * @return boolean  true if the element can be output
   */
  virtual bool CheckElementEnd(mozilla::dom::Element* aElement,
+                               mozilla::dom::Element* aOriginalElement,
                               bool& aForceFormat, nsAString& aStr);

  /**
--- a/dom/html/HTMLSlotElement.cpp
+++ b/dom/html/HTMLSlotElement.cpp
@ -154,26 +154,25 @@ const nsTArray<RefPtr<nsINode>>& HTMLSlotElement::AssignedNodes() const {
  return mAssignedNodes;
 }

-void HTMLSlotElement::InsertAssignedNode(uint32_t aIndex, nsINode* aNode) {
-  MOZ_ASSERT(!aNode->AsContent()->GetAssignedSlot(), "Losing track of a slot");
-  mAssignedNodes.InsertElementAt(aIndex, aNode);
-  aNode->AsContent()->SetAssignedSlot(this);
+void HTMLSlotElement::InsertAssignedNode(uint32_t aIndex, nsIContent& aNode) {
+  MOZ_ASSERT(!aNode.GetAssignedSlot(), "Losing track of a slot");
+  mAssignedNodes.InsertElementAt(aIndex, &aNode);
+  aNode.SetAssignedSlot(this);
 }

-void HTMLSlotElement::AppendAssignedNode(nsINode* aNode) {
-  MOZ_ASSERT(!aNode->AsContent()->GetAssignedSlot(), "Losing track of a slot");
-  mAssignedNodes.AppendElement(aNode);
-  aNode->AsContent()->SetAssignedSlot(this);
+void HTMLSlotElement::AppendAssignedNode(nsIContent& aNode) {
+  MOZ_ASSERT(!aNode.GetAssignedSlot(), "Losing track of a slot");
+  mAssignedNodes.AppendElement(&aNode);
+  aNode.SetAssignedSlot(this);
 }

-void HTMLSlotElement::RemoveAssignedNode(nsINode* aNode) {
+void HTMLSlotElement::RemoveAssignedNode(nsIContent& aNode) {
  // This one runs from unlinking, so we can't guarantee that the slot pointer
  // hasn't been cleared.
-  MOZ_ASSERT(!aNode->AsContent()->GetAssignedSlot() ||
-                 aNode->AsContent()->GetAssignedSlot() == this,
+  MOZ_ASSERT(!aNode.GetAssignedSlot() || aNode.GetAssignedSlot() == this,
             "How exactly?");
-  mAssignedNodes.RemoveElement(aNode);
-  aNode->AsContent()->SetAssignedSlot(nullptr);
+  mAssignedNodes.RemoveElement(&aNode);
+  aNode.SetAssignedSlot(nullptr);
 }

 void HTMLSlotElement::ClearAssignedNodes() {
--- a/dom/html/HTMLSlotElement.h
+++ b/dom/html/HTMLSlotElement.h
@ -54,9 +54,9 @@ class HTMLSlotElement final : public nsGenericHTMLElement {

  // Helper methods
  const nsTArray<RefPtr<nsINode>>& AssignedNodes() const;
-  void InsertAssignedNode(uint32_t aIndex, nsINode* aNode);
-  void AppendAssignedNode(nsINode* aNode);
-  void RemoveAssignedNode(nsINode* aNode);
+  void InsertAssignedNode(uint32_t aIndex, nsIContent&);
+  void AppendAssignedNode(nsIContent&);
+  void RemoveAssignedNode(nsIContent&);
  void ClearAssignedNodes();

  void EnqueueSlotChangeEvent();
--- a/dom/security/test/general/mochitest.ini
+++ b/dom/security/test/general/mochitest.ini
@ -47,6 +47,7 @@ skip-if = toolkit == 'android'
 [test_same_site_cookies_toplevel_nav.html]
 skip-if = fission # Crashes: @ mozilla::dom::ContentParent::CommonCreateWindow(mozilla::dom::PBrowserParent*, bool, unsigned int const&, bool const&, bool const&, bool const&, nsIURI*, nsTString<char> const&, float const&, unsigned long, nsTString<char16_t> const&, nsresult&, nsCOMPtr<nsIRemoteTab>&, bool*, int&, nsIPrincipal*, nsIReferrerInfo*, bool, nsIContentSecurityPolicy*)
 [test_same_site_cookies_cross_origin_context.html]
+fail-if = fission
 [test_same_site_cookies_from_script.html]
 [test_same_site_cookies_redirect.html]
 [test_same_site_cookies_toplevel_set_cookie.html]
--- a/dom/tests/mochitest/bugs/mochitest.ini
+++ b/dom/tests/mochitest/bugs/mochitest.ini
@ -156,7 +156,6 @@ skip-if = toolkit == 'android'
 [test_bug1112040.html]
 [test_bug1160342_marquee.html]
 [test_bug1171215.html]
-fail-if = fission
 support-files = window_bug1171215.html
 [test_bug1530292.html]
 fail-if = fission
--- a/dom/tests/mochitest/localstorage/mochitest.ini
+++ b/dom/tests/mochitest/localstorage/mochitest.ini
@ -27,6 +27,7 @@ skip-if = os == "android" || verify # bug 962029
 [test_cookieBlock.html]
 [test_embededNulls.html]
 [test_keySync.html]
+fail-if = fission
 [test_localStorageBase.html]
 skip-if = e10s
 [test_localStorageBaseSessionOnly.html]
@ -34,12 +35,17 @@ skip-if = e10s
 [test_localStorageEnablePref.html]
 [test_localStorageKeyOrder.html]
 [test_localStorageOriginsDiff.html]
+fail-if = fission
 [test_localStorageOriginsDomainDiffs.html]
+fail-if = fission
 [test_localStorageOriginsEquals.html]
 skip-if = toolkit == 'android'
+fail-if = fission
 [test_localStorageOriginsPortDiffs.html]
+fail-if = fission
 [test_localStorageOriginsSchemaDiffs.html]
 skip-if = toolkit == 'android' #TIMED_OUT
+fail-if = fission
 [test_localStorageQuota.html]
 skip-if = toolkit == 'android' #TIMED_OUT
 [test_localStorageQuotaSessionOnly.html]
--- a/dom/tests/mochitest/whatwg/mochitest.ini
+++ b/dom/tests/mochitest/whatwg/mochitest.ini
@ -25,15 +25,11 @@ support-files =
 skip-if = toolkit == 'android' #bug 894914 - wrong data - got FAIL, expected message
 [test_postMessage_hash.html]
 [test_postMessage.html]
-fail-if = fission
 [test_postMessage_idn.xhtml]
-fail-if = fission
 [test_postMessage_joined.html]
-fail-if = fission
 [test_postMessage_onOther.html]
 skip-if = fission #Bug 1571273
 [test_postMessage_origin.xhtml]
-fail-if = fission
 [test_postMessage_override.html]
 skip-if = fission
 [test_postMessage_special.xhtml]
@ -43,7 +39,6 @@ skip-if = fission #Bug 1570918
 [test_postMessage_transfer.html]
 skip-if = fission #Bug 1571208
 [test_postMessage_userpass.html]
-fail-if = fission
 [test_bug500328.html]
 skip-if = true || toolkit=='android' # bug 696306, #TIMED_OUT android
 support-files = file_bug500328_1.html file_bug500328_2.html
--- a/dom/websocket/tests/mochitest.ini
+++ b/dom/websocket/tests/mochitest.ini
@ -16,6 +16,7 @@ support-files =

 [test_bug1081686.html]
 [test_bug1384658.html]
+skip-if = fission # Timeouts
 support-files = window_bug1384658.html frame_bug1384658.html file_bug1384658.html
 [test_event_listener_leaks.html]
 support-files = file_websocket_bigBlob_wsh.py
--- a/dom/workers/test/mochitest.ini
+++ b/dom/workers/test/mochitest.ini
@ -145,6 +145,7 @@ tags = mcb
 [test_location.html]
 [test_longThread.html]
 [test_multi_sharedWorker.html]
+skip-if = fission # Timeouts
 [test_multi_sharedWorker_lifetimes.html]
 [test_navigator.html]
 support-files =
--- a/gfx/layers/ipc/LayersSurfaces.ipdlh
+++ b/gfx/layers/ipc/LayersSurfaces.ipdlh
@ -58,6 +58,16 @@ struct SurfaceDescriptorMacIOSurface {
  YUVColorSpace yUVColorSpace;
 };

+struct SurfaceDescriptorDMABuf {
+  uint32_t width;
+  uint32_t height;
+  uint32_t format;
+  uint32_t flags;
+  FileDescriptor fd;
+  uint32_t stride;
+  uint32_t offset;
+};
+
 struct SurfaceTextureDescriptor {
  uint64_t handle;
  IntSize size;
@ -148,6 +158,7 @@ union SurfaceDescriptor {
  SurfaceDescriptorFileMapping;
  SurfaceDescriptorDXGIYCbCr;
  SurfaceDescriptorX11;
+  SurfaceDescriptorDMABuf;
  SurfaceTextureDescriptor;
  EGLImageDescriptor;
  SurfaceDescriptorMacIOSurface;
--- a/js/moz.configure
+++ b/js/moz.configure
@ -439,7 +439,7 @@ set_define('JS_BUILD_BINAST', depends_if('--enable-binast')(lambda x: True))
 # ==============================================================

 js_option('--enable-cranelift',
-          default=milestone.is_nightly & js_standalone,
+          default=milestone.is_nightly,
          help='{Enable|Disable} Cranelift code generator for wasm')

 set_config('ENABLE_WASM_CRANELIFT', depends_if('--enable-cranelift')(lambda x: True))
--- a/js/src/frontend/SharedContext.h
+++ b/js/src/frontend/SharedContext.h
@ -291,6 +291,7 @@ struct LazyScriptCreationData {
    }

    if (!closedOverBindings.appendAll(COB)) {
+      ReportOutOfMemory(cx);  // closedOverBindings uses SystemAllocPolicy.
      return false;
    }
    return true;
--- a/js/src/jit-test/tests/parser/bug-1576865-1.js
+++ b/js/src/jit-test/tests/parser/bug-1576865-1.js
@ -0,0 +1,49 @@
+// |jit-test| skip-if: !('oomTest' in this)
+var sourceText = `
+  function Outer() {
+    var X00, X01, X02, X03, X04, X05, X06, X07;
+    var X08, X09, X10, X11, X12, X13, X14, X15;
+    var X16, X17, X18, X19, X20, X21, X22, X23;
+    var X24, X25, X26, X27, X28, X29, X30, X31;
+
+    function LazyFunction() {
+      // Lots of closed-over bindings.
+      { X00 = true; };
+      { X01 = true; };
+      { X02 = true; };
+      { X03 = true; };
+      { X04 = true; };
+      { X05 = true; };
+      { X06 = true; };
+      { X07 = true; };
+      { X08 = true; };
+      { X09 = true; };
+      { X10 = true; };
+      { X11 = true; };
+      { X12 = true; };
+      { X13 = true; };
+      { X14 = true; };
+      { X15 = true; };
+      { X16 = true; };
+      { X17 = true; };
+      { X18 = true; };
+      { X19 = true; };
+      { X20 = true; };
+      { X21 = true; };
+      { X22 = true; };
+      { X23 = true; };
+      { X24 = true; };
+      { X25 = true; };
+      { X26 = true; };
+      { X27 = true; };
+      { X28 = true; };
+      { X29 = true; };
+      { X30 = true; };
+      { X31 = true; };
+    }
+  }
+`;
+
+oomTest(function() {
+  evaluate(sourceText);
+  });
--- a/js/src/jit-test/tests/parser/bug-1576865-2.js
+++ b/js/src/jit-test/tests/parser/bug-1576865-2.js
@ -0,0 +1,44 @@
+// |jit-test| skip-if: !('oomTest' in this)
+var sourceText = `
+  function Outer() {
+    function LazyFunction() {
+      // Lots of inner functions.
+      function F00() { }
+      function F01() { }
+      function F02() { }
+      function F03() { }
+      function F04() { }
+      function F05() { }
+      function F06() { }
+      function F07() { }
+      function F08() { }
+      function F09() { }
+      function F10() { }
+      function F11() { }
+      function F12() { }
+      function F13() { }
+      function F14() { }
+      function F15() { }
+      function F16() { }
+      function F17() { }
+      function F18() { }
+      function F19() { }
+      function F20() { }
+      function F21() { }
+      function F22() { }
+      function F23() { }
+      function F24() { }
+      function F25() { }
+      function F26() { }
+      function F27() { }
+      function F28() { }
+      function F29() { }
+      function F30() { }
+      function F31() { }
+    }
+  }
+`;
+
+oomTest(function() {
+  evaluate(sourceText);
+  });
--- a/js/src/moz.build
+++ b/js/src/moz.build
@ -47,6 +47,9 @@ for stlfile in ['jsdate.*', 'jsnum.*']:
 with Files('builtin/intl/*'):
    BUG_COMPONENT = component_intl

+if CONFIG['ENABLE_WASM_CRANELIFT']:
+    CONFIGURE_SUBST_FILES += ['rust/extra-bindgen-flags']
+
 if not CONFIG['JS_DISABLE_SHELL']:
    DIRS += [
        'rust',
--- a/js/src/rust/moz.build
+++ b/js/src/rust/moz.build
@ -18,8 +18,6 @@ if CONFIG['ENABLE_WASM_CRANELIFT']:

 RustLibrary('jsrust', features)

-CONFIGURE_SUBST_FILES += ['extra-bindgen-flags']
-
 if CONFIG['JS_SHARED_LIBRARY']:
    FINAL_LIBRARY = 'js'

--- a/layout/painting/FrameLayerBuilder.cpp
+++ b/layout/painting/FrameLayerBuilder.cpp
@ -4012,9 +4012,7 @@ void PaintedLayerData::AccumulateHitTestItem(ContainerState* aState,
                                             nsDisplayItem* aItem,
                                             const DisplayItemClip& aClip,
                                             TransformClipNode* aTransform) {
-  MOZ_ASSERT(aItem->HasHitTestInfo());
  auto* item = static_cast<nsDisplayHitTestInfoItem*>(aItem);
-
  const HitTestInfo& info = item->GetHitTestInfo();

  nsRect area = info.mArea;
@ -4556,6 +4554,7 @@ void ContainerState::ProcessDisplayItems(nsDisplayList* aList) {
    nsRect itemContent;

    if (marker == DisplayItemEntryType::HitTestInfo) {
+      MOZ_ASSERT(item->IsHitTestItem());
      const auto& hitTestInfo =
          static_cast<nsDisplayHitTestInfoItem*>(item)->GetHitTestInfo();

--- a/layout/painting/nsDisplayList.h
+++ b/layout/painting/nsDisplayList.h
@ -3874,8 +3874,8 @@ struct HitTestInfo {
  nsRect mArea;
  mozilla::gfx::CompositorHitTestInfo mFlags;

-  AnimatedGeometryRoot* mAGR;
-  const mozilla::ActiveScrolledRoot* mASR;
+  RefPtr<AnimatedGeometryRoot> mAGR;
+  RefPtr<const mozilla::ActiveScrolledRoot> mASR;
  RefPtr<const mozilla::DisplayItemClipChain> mClipChain;
  const mozilla::DisplayItemClip* mClip;
 };
@ -3893,7 +3893,10 @@ class nsDisplayHitTestInfoItem : public nsPaintedDisplayItem {
                           const nsDisplayHitTestInfoItem& aOther)
      : nsPaintedDisplayItem(aBuilder, aOther) {}

-  const HitTestInfo& GetHitTestInfo() const { return *mHitTestInfo; }
+  const HitTestInfo& GetHitTestInfo() const {
+    MOZ_ASSERT(HasHitTestInfo());
+    return *mHitTestInfo;
+  }

  void SetActiveScrolledRoot(
      const ActiveScrolledRoot* aActiveScrolledRoot) override {
--- a/mobile/android/components/extensions/ext-tabs.js
+++ b/mobile/android/components/extensions/ext-tabs.js
@ -456,7 +456,9 @@ this.tabs = class extends ExtensionAPI {
          queryInfo = Object.assign({}, queryInfo);

          if (queryInfo.url !== null) {
-            queryInfo.url = new MatchPatternSet([].concat(queryInfo.url));
+            queryInfo.url = new MatchPatternSet([].concat(queryInfo.url), {
+              restrictSchemes: false,
+            });
          }
          if (queryInfo.title !== null) {
            queryInfo.title = new MatchGlob(queryInfo.title);
--- a/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/NavigationDelegateTest.kt
+++ b/mobile/android/geckoview/src/androidTest/java/org/mozilla/geckoview/test/NavigationDelegateTest.kt
@ -1240,4 +1240,41 @@ class NavigationDelegateTest : BaseSessionTest() {
        mainSession.loadTestPath(HELLO_HTML_PATH)
        sessionRule.waitForPageStop()
    }
+
+    @Test fun setLocationHash() {
+        sessionRule.session.loadUri("$TEST_ENDPOINT$HELLO_HTML_PATH")
+        sessionRule.waitForPageStop()
+
+        sessionRule.session.evaluateJS("location.hash = 'test1';")
+
+        sessionRule.session.waitUntilCalled(object : Callbacks.NavigationDelegate {
+            @AssertCalled(count = 0)
+            override fun onLoadRequest(session: GeckoSession,
+                                       request: LoadRequest):
+                                       GeckoResult<AllowOrDeny>? {
+                return null
+            }
+
+            @AssertCalled(count = 1)
+            override fun onLocationChange(session: GeckoSession, url: String?) {
+                assertThat("URI should match", url, endsWith("#test1"))
+            }
+        })
+
+        sessionRule.session.evaluateJS("location.hash = 'test2';")
+
+        sessionRule.session.waitUntilCalled(object : Callbacks.NavigationDelegate {
+            @AssertCalled(count = 0)
+            override fun onLoadRequest(session: GeckoSession,
+                                       request: LoadRequest):
+                                       GeckoResult<AllowOrDeny>? {
+                return null
+            }
+
+            @AssertCalled(count = 1)
+            override fun onLocationChange(session: GeckoSession, url: String?) {
+                assertThat("URI should match", url, endsWith("#test2"))
+            }
+        })
+    }
 }
--- a/netwerk/test/mochitests/mochitest.ini
+++ b/netwerk/test/mochitests/mochitest.ini
@ -83,6 +83,7 @@ skip-if = verify
 [test_1503201.html]
 [test_origin_header.html]
 [test_1502055.html]
+skip-if = fission # Timeouts
 support-files = sw_1502055.js file_1502055.sjs iframe_1502055.html
 [test_accept_header.html]
 support-files = test_accept_header.sjs
--- a/taskcluster/ci/source-test/mozlint.yml
+++ b/taskcluster/ci/source-test/mozlint.yml
@ -221,3 +221,45 @@ rustfmt:
    when:
        files-changed:
            - '**/*.rs'
+
+
+file-whitespace:
+    description: Check for trailing whitespaces and Windows CR
+    platform: lint/opt
+    treeherder:
+        symbol: file-whitespace
+    run:
+        mach: lint -l file-whitespace -f treeherder -f json:/builds/worker/mozlint.json
+    when:
+        files-changed:
+            - '**/*.c'
+            - '**/*.cc'
+            - '**/*.cpp'
+            - '**/*.h'
+            - '**/*.py'
+            - '**/*.rs'
+
+
+file-perm:
+    description: Check for incorrect permissions on source files
+    platform: lint/opt
+    treeherder:
+        symbol: file-perm
+    run:
+        mach: lint -l file-perm -f treeherder -f json:/builds/worker/mozlint.json
+    when:
+        files-changed:
+            - '**/*.c'
+            - '**/*.cc'
+            - '**/*.cpp'
+            - '**/*.h'
+            - '**/*.html'
+            - '**/*.js'
+            - '**/*.jsm'
+            - '**/*.jsx'
+            - '**/*.m'
+            - '**/*.mm'
+            - '**/*.rs'
+            - '**/*.xhtml'
+            - '**/*.xml'
+            - '**/*.xul'
--- a/taskcluster/taskgraph/transforms/job/init.py
+++ b/taskcluster/taskgraph/transforms/job/init.py
@ -238,7 +238,8 @@ def use_fetches(config, jobs):
                        extract = artifact.get('extract', True)

                    fetch = {
-                        'artifact': '{prefix}/{path}'.format(prefix=prefix, path=path),
+                        'artifact': '{prefix}/{path}'.format(prefix=prefix, path=path)
+                                    if not path.startswith('/') else path[1:],
                        'task': '<{dep}>'.format(dep=kind),
                        'extract': extract,
                    }
--- a/testing/web-platform/meta/css/css-multicol/multicol-breaking-005.html.ini
+++ b/testing/web-platform/meta/css/css-multicol/multicol-breaking-005.html.ini
@ -0,0 +1,2 @@
+[multicol-breaking-005.html]
+  prefs: [layout.css.column-span.enabled:true]
--- a/testing/web-platform/meta/css/css-multicol/multicol-breaking-nobackground-005.html.ini
+++ b/testing/web-platform/meta/css/css-multicol/multicol-breaking-nobackground-005.html.ini
@ -0,0 +1,2 @@
+[multicol-breaking-nobackground-005.html]
+  prefs: [layout.css.column-span.enabled:true]
--- a/testing/web-platform/tests/css/css-multicol/multicol-breaking-005-ref.html
+++ b/testing/web-platform/tests/css/css-multicol/multicol-breaking-005-ref.html
@ -0,0 +1,100 @@
+<!DOCTYPE HTML>
+<title>CSS Test Reference: breaking of a multicolumn</title>
+<meta charset="utf-8">
+<link rel="author" title="L. David Baron" href="https://dbaron.org/">
+<link rel="author" title="Ting-Yu Lin" href="tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://mozilla.org/">
+<style>
+
+.outer {
+  height: 200px;
+  width: 800px;
+  background: rgba(0, 0, 255, 0.3);
+  position: relative;
+}
+
+.blueborders {
+  position: absolute;
+  top: 0;
+  left: 262px; /* 256px first column + (16px gap - 4px rule) / 2 */
+  width: 268px; /* 256px second column + (16px gap - 4px rule) */
+  height: 200px;
+  border-right: blue solid 4px;
+  border-left: blue solid 4px;
+}
+
+.innerbg {
+  height: 100px;
+  width: 256px;
+  background: rgba(255, 0, 255, 0.3);
+  position: absolute;
+  top: 0;
+}
+
+.inner {
+  height: 100px;
+  width: 120px;
+  font: 16px/1.25 sans-serif;
+  position: absolute;
+  top: 0;
+}
+
+.lefthalf {
+  border-right: 2px solid fuchsia;
+  padding-right: 7px;
+}
+
+.righthalf {
+  padding-left: 7px;
+}
+
+</style>
+
+<div class="outer">
+  <div class="blueborders"></div>
+  <div class="innerbg" style="left: 0"></div>
+  <div class="inner lefthalf" style="left: 0">
+    AAAAA<br>
+    BBBBB<br>
+    CCCCC<br>
+    DDDDD<br>
+    EEEEE
+  </div>
+  <div class="inner righthalf" style="left: 129px">
+    FFFFF<br>
+    GGGGG<br>
+    HHHHH<br>
+    IIIII<br>
+    JJJJJ
+  </div>
+  <div class="innerbg" style="left: 272px"></div>
+  <div class="inner lefthalf" style="left: 272px">
+    KKKKK<br>
+    LLLLL<br>
+    MMMMM<br>
+    NNNNN<br>
+    OOOOO
+  </div>
+  <div class="inner righthalf" style="left: 401px">
+    PPPPP<br>
+    QQQQQ<br>
+    RRRRR<br>
+    SSSSS<br>
+    TTTTT
+  </div>
+  <div class="innerbg" style="left: 544px"></div>
+  <div class="inner lefthalf" style="left: 544px">
+    UUUUU<br>
+    VVVVV<br>
+    WWWWW<br>
+    XXXXX<br>
+    YYYYY
+  </div>
+  <div class="inner righthalf" style="left: 673px">
+    ZZZZZ<br>
+    aaaaa<br>
+    bbbbb<br>
+    ccccc<br>
+    ddddd
+  </div>
+</div>
--- a/testing/web-platform/tests/css/css-multicol/multicol-breaking-005.html
+++ b/testing/web-platform/tests/css/css-multicol/multicol-breaking-005.html
@ -0,0 +1,70 @@
+<!DOCTYPE HTML>
+<title>CSS Test: breaking of a multicolumn</title>
+<meta charset="utf-8">
+<link rel="author" title="L. David Baron" href="https://dbaron.org/">
+<link rel="author" title="Ting-Yu Lin" href="tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://mozilla.org/">
+<link rel="help" href="https://drafts.csswg.org/css-multicol/#column-gaps-and-rules">
+<link rel="help" href="https://drafts.csswg.org/css-multicol/#cf">
+<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/2309">
+<link rel="match" href="multicol-breaking-005-ref.html">
+<style>
+
+.outer {
+  height: 200px;
+  width: 800px;
+  column-fill: balance;
+  column-count: 3;
+  column-rule: 4px solid blue;
+  column-gap: 16px;
+  background: rgba(0, 0, 255, 0.3);
+}
+
+.inner {
+  column-count: 2;
+  column-fill: balance;
+  column-rule: 2px solid fuchsia;
+  column-gap: 16px;
+  background: rgba(255, 0, 255, 0.3);
+  font: 16px/1.25 sans-serif;
+}
+
+</style>
+
+<!-- This test is similar to multicol-breaking-002.html,
+     but both outer and inner columns are balancing. The outer multi-column is
+     made explicitly taller than the inner columns' optimal balance height. -->
+<div class="outer">
+  <div class="inner" style="height: 300px">
+    AAAAA<br>
+    BBBBB<br>
+    CCCCC<br>
+    DDDDD<br>
+    EEEEE<br>
+    FFFFF<br>
+    GGGGG<br>
+    HHHHH<br>
+    IIIII<br>
+    JJJJJ<br>
+    KKKKK<br>
+    LLLLL<br>
+    MMMMM<br>
+    NNNNN<br>
+    OOOOO<br>
+    PPPPP<br>
+    QQQQQ<br>
+    RRRRR<br>
+    SSSSS<br>
+    TTTTT<br>
+    UUUUU<br>
+    VVVVV<br>
+    WWWWW<br>
+    XXXXX<br>
+    YYYYY<br>
+    ZZZZZ<br>
+    aaaaa<br>
+    bbbbb<br>
+    ccccc<br>
+    ddddd
+  </div>
+</div>
--- a/testing/web-platform/tests/css/css-multicol/multicol-breaking-nobackground-005-ref.html
+++ b/testing/web-platform/tests/css/css-multicol/multicol-breaking-nobackground-005-ref.html
@ -0,0 +1,86 @@
+<!DOCTYPE HTML>
+<title>CSS Test Reference: breaking of a multicolumn</title>
+<meta charset="utf-8">
+<link rel="author" title="L. David Baron" href="https://dbaron.org/">
+<link rel="author" title="Ting-Yu Lin" href="tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://mozilla.org/">
+<style>
+
+.outer {
+  height: 200px;
+  width: 800px;
+  background: rgba(0, 0, 255, 0.3);
+  position: relative;
+}
+
+.innerbg {
+  height: 100px;
+  width: 256px;
+  background: rgba(255, 0, 255, 0.3);
+  position: absolute;
+  top: 0;
+}
+
+.inner {
+  height: 100px;
+  width: 120px;
+  font: 16px/1.25 sans-serif;
+  position: absolute;
+  top: 0;
+}
+
+.lefthalf {
+  border-right: 2px solid fuchsia;
+  padding-right: 7px;
+}
+
+.righthalf {
+  padding-left: 7px;
+}
+
+</style>
+
+<div class="outer">
+  <div class="inner lefthalf" style="left: 0">
+    AAAAA<br>
+    BBBBB<br>
+    CCCCC<br>
+    DDDDD<br>
+    EEEEE
+  </div>
+  <div class="inner righthalf" style="left: 129px">
+    FFFFF<br>
+    GGGGG<br>
+    HHHHH<br>
+    IIIII<br>
+    JJJJJ
+  </div>
+  <div class="inner lefthalf" style="left: 272px">
+    KKKKK<br>
+    LLLLL<br>
+    MMMMM<br>
+    NNNNN<br>
+    OOOOO
+  </div>
+  <div class="inner righthalf" style="left: 401px">
+    PPPPP<br>
+    QQQQQ<br>
+    RRRRR<br>
+    SSSSS<br>
+    TTTTT
+  </div>
+  <div class="inner lefthalf" style="left: 544px">
+    UUUUU<br>
+    VVVVV<br>
+    WWWWW<br>
+    XXXXX<br>
+    YYYYY
+  </div>
+  <div class="inner righthalf" style="left: 673px">
+    ZZZZZ<br>
+    aaaaa<br>
+    bbbbb<br>
+    ccccc<br>
+    ddddd
+  </div>
+</div>
--- a/testing/web-platform/tests/css/css-multicol/multicol-breaking-nobackground-005.html
+++ b/testing/web-platform/tests/css/css-multicol/multicol-breaking-nobackground-005.html
@ -0,0 +1,68 @@
+<!DOCTYPE HTML>
+<title>CSS Test: breaking of a multicolumn</title>
+<meta charset="utf-8">
+<link rel="author" title="L. David Baron" href="https://dbaron.org/">
+<link rel="author" title="Ting-Yu Lin" href="tlin@mozilla.com">
+<link rel="author" title="Mozilla" href="https://mozilla.org/">
+<link rel="help" href="https://drafts.csswg.org/css-multicol/#column-gaps-and-rules">
+<link rel="help" href="https://drafts.csswg.org/css-multicol/#cf">
+<link rel="help" href="https://github.com/w3c/csswg-drafts/issues/2309">
+<link rel="match" href="multicol-breaking-nobackground-005-ref.html">
+<style>
+
+.outer {
+  height: 200px;
+  width: 800px;
+  column-fill: balance;
+  column-count: 3;
+  column-gap: 16px;
+  background: rgba(0, 0, 255, 0.3);
+}
+
+.inner {
+  column-count: 2;
+  column-fill: balance;
+  column-rule: 2px solid fuchsia;
+  column-gap: 16px;
+  font: 16px/1.25 sans-serif;
+}
+
+</style>
+
+<!-- This test is similar to multicol-breaking-nobackground-002.html,
+     but both outer and inner columns are balancing. The outer multi-column is
+     made explicitly taller than the inner columns' optimal balance height. -->
+<div class="outer">
+  <div class="inner" style="height: 300px">
+    AAAAA<br>
+    BBBBB<br>
+    CCCCC<br>
+    DDDDD<br>
+    EEEEE<br>
+    FFFFF<br>
+    GGGGG<br>
+    HHHHH<br>
+    IIIII<br>
+    JJJJJ<br>
+    KKKKK<br>
+    LLLLL<br>
+    MMMMM<br>
+    NNNNN<br>
+    OOOOO<br>
+    PPPPP<br>
+    QQQQQ<br>
+    RRRRR<br>
+    SSSSS<br>
+    TTTTT<br>
+    UUUUU<br>
+    VVVVV<br>
+    WWWWW<br>
+    XXXXX<br>
+    YYYYY<br>
+    ZZZZZ<br>
+    aaaaa<br>
+    bbbbb<br>
+    ccccc<br>
+    ddddd
+  </div>
+</div>
--- a/third_party/rust/dogear/.cargo-checksum.json
+++ b/third_party/rust/dogear/.cargo-checksum.json
@ -1 +1 @@
-{"files":{"CODE_OF_CONDUCT.md":"e85149c44f478f164f7d5f55f6e66c9b5ae236d4a11107d5e2a93fe71dd874b9","Cargo.toml":"cfc0416b0a1c11ade3b5c11ec579c8e26ed3fc3b5871dd99d4fbcc12bd2614d0","LICENSE":"c71d239df91726fc519c6eb72d318ec65820627232b2f796219e87dcf35d0ab4","README.md":"303ea5ec53d4e86f2c321056e8158e31aa061353a99e52de3d76859d40919efc","src/driver.rs":"913de08a578b38902f4eb0d78147289897af5d3b1ecdad818c4ea6f83da6c714","src/error.rs":"d4ef0cba5c7fc54959ed62da166f10435548d705e0a817eed449fb001fe4e21d","src/guid.rs":"c82af64fba3ad87948a9b599241e48753d17587e8c642f610949163be3d499bf","src/lib.rs":"0606e69b235650bf404ae0b03a1e85c2063bb4b7147fa4d5e8ff2c128a757453","src/merge.rs":"e74727171831585d304eee3a3c7ba24fec52a5e7c6999ed4e647fefa14b8be99","src/store.rs":"629410e44485c0473617911be0e06dc5ce504c7427782be02f05a2f4096b5351","src/tests.rs":"51bc77eb989974f7594dfa0cdf7741f8e26f2956eebc34d1f71cbfd137512940","src/tree.rs":"fcdc9a5ae0e3f1b0d62d01bf1024db2a0aa8660e6839ada607a6a20e0fe2ad83"},"package":"251a15c9a597d70eb53cbb0c5473d8d8c6241aef615c092030ebab27fb5b26ef"}
+{"files":{"CODE_OF_CONDUCT.md":"e85149c44f478f164f7d5f55f6e66c9b5ae236d4a11107d5e2a93fe71dd874b9","Cargo.toml":"9c145c9ecdad0143f95fb00d5646fb3f46203779a201f2f2389961563ca37397","LICENSE":"c71d239df91726fc519c6eb72d318ec65820627232b2f796219e87dcf35d0ab4","README.md":"303ea5ec53d4e86f2c321056e8158e31aa061353a99e52de3d76859d40919efc","src/driver.rs":"913de08a578b38902f4eb0d78147289897af5d3b1ecdad818c4ea6f83da6c714","src/error.rs":"d4ef0cba5c7fc54959ed62da166f10435548d705e0a817eed449fb001fe4e21d","src/guid.rs":"c82af64fba3ad87948a9b599241e48753d17587e8c642f610949163be3d499bf","src/lib.rs":"0606e69b235650bf404ae0b03a1e85c2063bb4b7147fa4d5e8ff2c128a757453","src/merge.rs":"bfc83aa6f42c196a5c6c75e095d1e44470198a38f3a62a6537cd5854d51208cd","src/store.rs":"629410e44485c0473617911be0e06dc5ce504c7427782be02f05a2f4096b5351","src/tests.rs":"fd2f03fd47e02459b7a3c7f799896be71536054184a2eca7e30cdbe817da0a97","src/tree.rs":"30c7d0c80f180936d1f99d2a3fbe9add36f3fe36a64998e3176d0242f425c488"},"package":"57cd6ee785daa898686f3e2fb4a2b1ce490fcd6d69665c857d16fb61b48f4aae"}
--- a/third_party/rust/dogear/Cargo.toml
+++ b/third_party/rust/dogear/Cargo.toml
@ -13,7 +13,7 @@
 [package]
 edition = "2018"
 name = "dogear"
-version = "0.3.1"
+version = "0.3.3"
 authors = ["Lina Cambridge <lina@mozilla.com>"]
 exclude = ["/.travis/**", ".travis.yml", "/docs/**", "book.toml"]
 description = "A library for merging bookmark trees."
--- a/third_party/rust/dogear/src/merge.rs
+++ b/third_party/rust/dogear/src/merge.rs
@ -1528,28 +1528,23 @@ impl<'t, D: Driver, A: AbortSignal> Merger<'t, D, A> {
        for (local_position, local_child_node) in local_parent_node.children().enumerate() {
            self.signal.err_if_aborted()?;
            if local_child_node.is_built_in_root() {
-                continue;
-            }
-            if let Some(local_child_content) = local_child_node.content() {
-                if let Some(remote_child_node) =
-                    self.remote_tree.node_for_guid(&local_child_node.guid)
-                {
                trace!(
                    self.driver,
-                        "Not deduping local child {}; already exists remotely as {}",
-                        local_child_node,
-                        remote_child_node
-                    );
-                    continue;
-                }
-                if self.remote_tree.is_deleted(&local_child_node.guid) {
-                    trace!(
-                        self.driver,
-                        "Not deduping local child {}; deleted remotely",
+                    "Not deduping local built-in root {}",
                    local_child_node
                );
                continue;
            }
+            if self.remote_tree.mentions(&local_child_node.guid) {
+                trace!(
+                    self.driver,
+                    "Not deduping local child {}; already deleted or exists remotely",
+                    local_child_node
+                );
+                continue;
+            }
+            match local_child_node.content() {
+                Some(local_child_content) => {
                    // Store matching local children in an array, in case multiple children
                    // have the same dupe key (for example, a toolbar containing multiple
                    // empty folders, as in bug 1213369).
@ -1563,20 +1558,38 @@ impl<'t, D: Driver, A: AbortSignal> Merger<'t, D, A> {
                    };
                    let local_nodes_for_key = dupe_key_to_local_nodes.entry(dupe_key).or_default();
                    local_nodes_for_key.push_back(local_child_node);
-            } else {
+                }
+                None => {
                    trace!(
                        self.driver,
-                    "Not deduping local child {}; already uploaded",
+                        "Not deduping local child {} without content info",
                        local_child_node
                    );
                }
            }
+        }

        let mut local_to_remote = HashMap::new();
        let mut remote_to_local = HashMap::new();

        for (remote_position, remote_child_node) in remote_parent_node.children().enumerate() {
            self.signal.err_if_aborted()?;
+            if remote_child_node.is_built_in_root() {
+                trace!(
+                    self.driver,
+                    "Not deduping remote built-in root {}",
+                    remote_child_node
+                );
+                continue;
+            }
+            if self.local_tree.mentions(&remote_child_node.guid) {
+                trace!(
+                    self.driver,
+                    "Not deduping remote child {}; already deleted or exists locally",
+                    remote_child_node
+                );
+                continue;
+            }
            if remote_to_local.contains_key(&remote_child_node.guid) {
                trace!(
                    self.driver,
@ -1588,7 +1601,8 @@ impl<'t, D: Driver, A: AbortSignal> Merger<'t, D, A> {
            // Note that we don't need to check if the remote node is deleted
            // locally, because it wouldn't have local content entries if it
            // were.
-            if let Some(remote_child_content) = remote_child_node.content() {
+            match remote_child_node.content() {
+                Some(remote_child_content) => {
                    let dupe_key = match remote_child_content {
                        Content::Bookmark { .. } | Content::Folder { .. } => {
                            DupeKey::WithoutPosition(remote_child_content)
@ -1605,8 +1619,10 @@ impl<'t, D: Driver, A: AbortSignal> Merger<'t, D, A> {
                                local_child_node,
                                remote_child_node
                            );
-                        local_to_remote.insert(local_child_node.guid.clone(), remote_child_node);
-                        remote_to_local.insert(remote_child_node.guid.clone(), local_child_node);
+                            local_to_remote
+                                .insert(local_child_node.guid.clone(), remote_child_node);
+                            remote_to_local
+                                .insert(remote_child_node.guid.clone(), local_child_node);
                        } else {
                            trace!(
                                self.driver,
@ -1623,14 +1639,16 @@ impl<'t, D: Driver, A: AbortSignal> Merger<'t, D, A> {
                        );
                        continue;
                    }
-            } else {
+                }
+                None => {
                    trace!(
                        self.driver,
-                    "Not deduping remote child {}; already merged",
+                        "Not deduping remote child {} without content info",
                        remote_child_node
                    );
                }
            }
+        }

        Ok((local_to_remote, remote_to_local))
    }
--- a/third_party/rust/dogear/src/tests.rs
+++ b/third_party/rust/dogear/src/tests.rs
@ -60,7 +60,7 @@ impl TryFrom<Node> for Builder {
                    _ => return Err(err),
                }
            }
-            b.mutate(&guid).by_structure(&parent_guid)?;
+            b.parent_for(&guid).by_structure(&parent_guid)?;
            for child in node.children {
                inflate(b, &guid, child)?;
            }
@ -1323,6 +1323,82 @@ fn newer_move_to_deleted() {
    assert_eq!(merged_root.counts(), &expected_telem);
 }

+#[test]
+fn deduping_multiple_candidates() {
+    before_each();
+
+    let mut local_tree_builder = Builder::try_from(nodes!({
+        ("menu________", Folder[needs_merge = true, age = 5], {
+            ("folderAAAAA1", Folder[needs_merge = true, age = 5]),
+            ("folderAAAAA2", Folder[needs_merge = true, age = 5])
+        }),
+        ("toolbar_____", Folder[needs_merge = true], {
+            ("folderBBBBB1", Folder[needs_merge = true])
+        })
+    }))
+    .unwrap();
+    local_tree_builder
+        .mutate(&"folderAAAAA1".into())
+        .content(Content::Folder { title: "A".into() });
+    local_tree_builder
+        .mutate(&"folderAAAAA2".into())
+        .content(Content::Folder { title: "A".into() });
+    local_tree_builder
+        .mutate(&"folderBBBBB1".into())
+        .content(Content::Folder { title: "B".into() });
+    let local_tree = local_tree_builder.into_tree().unwrap();
+
+    let mut remote_tree_builder = Builder::try_from(nodes!({
+        ("menu________", Folder[needs_merge = true], {
+            ("folderAAAAA1", Folder[needs_merge = true])
+        }),
+        ("toolbar_____", Folder[needs_merge = true, age = 5], {
+            ("folderBBBBB1", Folder[needs_merge = true, age = 5]),
+            ("folderBBBBB2", Folder[needs_merge = true, age = 5])
+        })
+    }))
+    .unwrap();
+    remote_tree_builder
+        .mutate(&"folderAAAAA1".into())
+        .content(Content::Folder { title: "A".into() });
+    remote_tree_builder
+        .mutate(&"folderBBBBB1".into())
+        .content(Content::Folder { title: "B".into() });
+    remote_tree_builder
+        .mutate(&"folderBBBBB2".into())
+        .content(Content::Folder { title: "B".into() });
+    let remote_tree = remote_tree_builder.into_tree().unwrap();
+
+    let merger = Merger::new(&local_tree, &remote_tree);
+    let merged_root = merger.merge().unwrap();
+
+    let expected_tree = merged_nodes!({
+        ("menu________", LocalWithNewLocalStructure, {
+            ("folderAAAAA1", Remote),
+            ("folderAAAAA2", Local)
+        }),
+        ("toolbar_____", LocalWithNewLocalStructure, {
+            ("folderBBBBB1", Local),
+            ("folderBBBBB2", Remote)
+        })
+    });
+    let expected_telem = StructureCounts {
+        remote_revives: 0,
+        local_deletes: 0,
+        local_revives: 0,
+        remote_deletes: 0,
+        dupes: 0,
+        merged_nodes: 6,
+        merged_deletions: 0,
+    };
+
+    assert_eq!(&expected_tree, merged_root.node());
+
+    assert_eq!(merged_root.deletions().count(), 0);
+
+    assert_eq!(merged_root.counts(), &expected_telem);
+}
+
 #[test]
 fn deduping_local_newer() {
    before_each();
--- a/third_party/rust/dogear/src/tree.rs
+++ b/third_party/rust/dogear/src/tree.rs
@ -499,52 +499,10 @@ impl<'b> ItemBuilder<'b> {
        b.by_parent_guid(parent_guid)
    }

-    /// Records a `parent_guid` from a valid tree structure. This is for
-    /// callers who already know their structure is consistent, like
-    /// `Store::fetch_local_tree()` on Desktop, and
-    /// `std::convert::TryInto<Tree>` in the tests.
-    ///
-    /// Both the item and `parent_guid` must exist, and the `parent_guid` must
-    /// refer to a folder.
-    ///
-    /// `by_structure(parent_guid)` is logically the same as:
-    ///
-    /// ```no_run
-    /// # use dogear::{Item, Kind, Result, ROOT_GUID, Tree};
-    /// # fn main() -> Result<()> {
-    /// # let mut builder = Tree::with_root(Item::new(ROOT_GUID, Kind::Folder));
-    /// # let child_guid = "bookmarkAAAA".into();
-    /// # let parent_guid = "folderAAAAAA".into();
-    /// builder.parent_for(&child_guid)
-    ///     .by_children(&parent_guid)?
-    /// .parent_for(&child_guid)
-    ///     .by_parent_guid(parent_guid)?;
-    /// # Ok(())
-    /// # }
-    /// ```
-    ///
-    /// ...But more convenient. It's also more efficient, because it avoids
-    /// multiple lookups for the item and parent, as well as an extra heap
-    /// allocation to store the parents.
+    #[inline]
    pub fn by_structure(self, parent_guid: &Guid) -> Result<&'b mut Builder> {
-        let parent_index = match self.0.entry_index_by_guid.get(parent_guid) {
-            Some(&parent_index) if self.0.entries[parent_index].item.is_folder() => parent_index,
-            _ => {
-                return Err(ErrorKind::InvalidParent(
-                    self.0.entries[self.1].item.guid.clone(),
-                    parent_guid.clone(),
-                )
-                .into());
-            }
-        };
-        self.0.entries[self.1].parents_by(&[
-            BuilderParentBy::Children(parent_index),
-            BuilderParentBy::KnownItem(parent_index),
-        ])?;
-        self.0.entries[parent_index]
-            .children
-            .push(BuilderEntryChild::Exists(self.1));
-        Ok(self.0)
+        let b = ParentBuilder(self.0, BuilderEntryChild::Exists(self.1));
+        b.by_structure(parent_guid)
    }
 }

@ -593,6 +551,56 @@ impl<'b> ParentBuilder<'b> {
        }
        Ok(self.0)
    }
+
+    /// Records a `parent_guid` from a valid tree structure. This is for
+    /// callers who already know their structure is consistent, like
+    /// `Store::fetch_local_tree()` on Desktop, and
+    /// `std::convert::TryInto<Tree>` in the tests.
+    ///
+    /// Both the item and `parent_guid` must exist, and the `parent_guid` must
+    /// refer to a folder.
+    ///
+    /// `by_structure(parent_guid)` is logically the same as:
+    ///
+    /// ```no_run
+    /// # use dogear::{Item, Kind, Result, ROOT_GUID, Tree};
+    /// # fn main() -> Result<()> {
+    /// # let mut builder = Tree::with_root(Item::new(ROOT_GUID, Kind::Folder));
+    /// # let child_guid = "bookmarkAAAA".into();
+    /// # let parent_guid = "folderAAAAAA".into();
+    /// builder.parent_for(&child_guid)
+    ///     .by_children(&parent_guid)?
+    /// .parent_for(&child_guid)
+    ///     .by_parent_guid(parent_guid)?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    ///
+    /// ...But more convenient. It's also more efficient, because it avoids
+    /// multiple lookups for the item and parent, as well as an extra heap
+    /// allocation to store the parents.
+    pub fn by_structure(self, parent_guid: &Guid) -> Result<&'b mut Builder> {
+        let parent_index = match self.0.entry_index_by_guid.get(parent_guid) {
+            Some(&parent_index) if self.0.entries[parent_index].item.is_folder() => parent_index,
+            _ => {
+                let child_guid = match &self.1 {
+                    BuilderEntryChild::Exists(index) => &self.0.entries[*index].item.guid,
+                    BuilderEntryChild::Missing(guid) => guid,
+                };
+                return Err(
+                    ErrorKind::InvalidParent(child_guid.clone(), parent_guid.clone()).into(),
+                );
+            }
+        };
+        if let BuilderEntryChild::Exists(child_index) = &self.1 {
+            self.0.entries[*child_index].parents_by(&[
+                BuilderParentBy::Children(parent_index),
+                BuilderParentBy::KnownItem(parent_index),
+            ])?;
+        }
+        self.0.entries[parent_index].children.push(self.1);
+        Ok(self.0)
+    }
 }

 /// An entry wraps a tree item with references to its parents and children,
--- a/Показать больше
+++ b/Показать больше