diff --git a/browser/base/content/browser-sync.js b/browser/base/content/browser-sync.js
index dd109a2a66e0..831e2dc28a36 100644
--- a/browser/base/content/browser-sync.js
+++ b/browser/base/content/browser-sync.js
@@ -1212,6 +1212,12 @@ var gSync = {
     if (confirm && !(await this._confirmDisconnect(disconnectAccount))) {
       return false;
     }
+    // Record telemetry.
+    await fxAccounts.telemetry.recordDisconnection(
+      disconnectAccount ? null : "sync",
+      "ui"
+    );
+
     await Weave.Service.promiseInitialized;
     await Weave.Service.startOver();
     if (disconnectAccount) {
diff --git a/browser/components/originattributes/test/browser/browser.ini b/browser/components/originattributes/test/browser/browser.ini
index b24fa3032437..1c3ea556ba0c 100644
--- a/browser/components/originattributes/test/browser/browser.ini
+++ b/browser/components/originattributes/test/browser/browser.ini
@@ -81,6 +81,7 @@ skip-if = fission
 skip-if = (verify && debug && (os == 'win'))
 [browser_imageCacheIsolation.js]
 [browser_sharedworker.js]
+skip-if = fission #Bug 1582318
 [browser_httpauth.js]
 [browser_clientAuth.js]
 skip-if = verify
diff --git a/browser/components/preferences/in-content/sync.js b/browser/components/preferences/in-content/sync.js
index bee2fda9822d..02c5251ff3d2 100644
--- a/browser/components/preferences/in-content/sync.js
+++ b/browser/components/preferences/in-content/sync.js
@@ -302,7 +302,14 @@ var gSyncPane = {
         if (!isAlreadySyncing && event.detail.button == "accept") {
           // We weren't syncing but the user has accepted the dialog - so we
           // want to start!
-          Weave.Service.configure();
+          fxAccounts.telemetry
+            .recordConnection(["sync"], "ui")
+            .then(() => {
+              return Weave.Service.configure();
+            })
+            .catch(err => {
+              console.error("Failed to enable sync", err);
+            });
         }
       }
     );
diff --git a/devtools/client/inspector/compatibility/CompatibilityView.js b/devtools/client/inspector/compatibility/CompatibilityView.js
index b79947c4f77c..41c8a9e59292 100644
--- a/devtools/client/inspector/compatibility/CompatibilityView.js
+++ b/devtools/client/inspector/compatibility/CompatibilityView.js
@@ -80,16 +80,18 @@ class CompatibilityView {
     );
   }
 
-  _isVisible() {
+  _isAvailable() {
     return (
       this.inspector &&
       this.inspector.sidebar &&
-      this.inspector.sidebar.getCurrentTabID() === "compatibilityview"
+      this.inspector.sidebar.getCurrentTabID() === "compatibilityview" &&
+      this.inspector.selection &&
+      this.inspector.selection.isConnected()
     );
   }
 
   _onNewNode() {
-    if (!this._isVisible()) {
+    if (!this._isAvailable()) {
       return;
     }
 
diff --git a/devtools/client/inspector/compatibility/actions/compatibility.js b/devtools/client/inspector/compatibility/actions/compatibility.js
index 51192476a25f..3ed7764ccd09 100644
--- a/devtools/client/inspector/compatibility/actions/compatibility.js
+++ b/devtools/client/inspector/compatibility/actions/compatibility.js
@@ -5,19 +5,35 @@
 "use strict";
 
 const {
-  COMPATIBILITY_UPDATE_SELECTED_NODE,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_START,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_SUCCESS,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE,
   COMPATIBILITY_UPDATE_TARGET_BROWSERS,
 } = require("./index");
 
 function updateSelectedNode(nodeFront) {
   return async ({ dispatch }) => {
-    const pageStyle = nodeFront.inspectorFront.pageStyle;
-    const styles = await pageStyle.getApplied(nodeFront, { skipPseudo: false });
-    const declarationBlocks = styles
-      .map(({ rule }) => rule.declarations.filter(d => !d.commentOffsets))
-      .filter(declarations => declarations.length);
+    dispatch({ type: COMPATIBILITY_UPDATE_SELECTED_NODE_START });
 
-    dispatch({ type: COMPATIBILITY_UPDATE_SELECTED_NODE, declarationBlocks });
+    try {
+      const pageStyle = nodeFront.inspectorFront.pageStyle;
+      const styles = await pageStyle.getApplied(nodeFront, {
+        skipPseudo: false,
+      });
+      const declarationBlocks = styles
+        .map(({ rule }) => rule.declarations.filter(d => !d.commentOffsets))
+        .filter(declarations => declarations.length);
+
+      dispatch({
+        type: COMPATIBILITY_UPDATE_SELECTED_NODE_SUCCESS,
+        declarationBlocks,
+      });
+    } catch (error) {
+      dispatch({ type: COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE, error });
+    }
+
+    dispatch({ type: COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE });
   };
 }
 
diff --git a/devtools/client/inspector/compatibility/actions/index.js b/devtools/client/inspector/compatibility/actions/index.js
index e21abbda587d..5d88a996cc3d 100644
--- a/devtools/client/inspector/compatibility/actions/index.js
+++ b/devtools/client/inspector/compatibility/actions/index.js
@@ -9,7 +9,10 @@ const { createEnum } = require("devtools/client/shared/enum");
 createEnum(
   [
     // Updates the selected node.
-    "COMPATIBILITY_UPDATE_SELECTED_NODE",
+    "COMPATIBILITY_UPDATE_SELECTED_NODE_START",
+    "COMPATIBILITY_UPDATE_SELECTED_NODE_SUCCESS",
+    "COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE",
+    "COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE",
 
     // Updates the target browsers.
     "COMPATIBILITY_UPDATE_TARGET_BROWSERS",
diff --git a/devtools/client/inspector/compatibility/reducers/compatibility.js b/devtools/client/inspector/compatibility/reducers/compatibility.js
index 4ddf20444ea2..9cea5b214cc7 100644
--- a/devtools/client/inspector/compatibility/reducers/compatibility.js
+++ b/devtools/client/inspector/compatibility/reducers/compatibility.js
@@ -11,7 +11,8 @@ loader.lazyGetter(this, "mdnCompatibility", () => {
 });
 
 const {
-  COMPATIBILITY_UPDATE_SELECTED_NODE,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_SUCCESS,
+  COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE,
   COMPATIBILITY_UPDATE_TARGET_BROWSERS,
 } = require("../actions/index");
 
@@ -22,9 +23,16 @@ const INITIAL_STATE = {
 };
 
 const reducers = {
-  [COMPATIBILITY_UPDATE_SELECTED_NODE](state, data) {
+  [COMPATIBILITY_UPDATE_SELECTED_NODE_SUCCESS](state, data) {
     return updateSelectedNodeIssues(state, data);
   },
+  [COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE](state, { error }) {
+    console.error(
+      `[COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE] ${error.message}`
+    );
+    console.error(error.stack);
+    return state;
+  },
   [COMPATIBILITY_UPDATE_TARGET_BROWSERS](state, data) {
     return updateSelectedNodeIssues(state, data);
   },
diff --git a/devtools/client/inspector/compatibility/test/browser/browser.ini b/devtools/client/inspector/compatibility/test/browser/browser.ini
index 44eb9b4e55fc..f2205a99a88a 100644
--- a/devtools/client/inspector/compatibility/test/browser/browser.ini
+++ b/devtools/client/inspector/compatibility/test/browser/browser.ini
@@ -12,6 +12,7 @@ support-files =
 
 [browser_compatibility_css-property_issue.js]
 [browser_compatibility_event_new-node.js]
+[browser_compatibility_event_new-node_without-connection.js]
 [browser_compatibility_event_rule-change.js]
 [browser_compatibility_preference.js]
 [browser_compatibility_unsupported-browsers_all.js]
diff --git a/devtools/client/inspector/compatibility/test/browser/browser_compatibility_event_new-node_without-connection.js b/devtools/client/inspector/compatibility/test/browser/browser_compatibility_event_new-node_without-connection.js
new file mode 100644
index 000000000000..c2d5b22868e6
--- /dev/null
+++ b/devtools/client/inspector/compatibility/test/browser/browser_compatibility_event_new-node_without-connection.js
@@ -0,0 +1,32 @@
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+// Test whether no errors occur when reloading the browsing page.
+
+const {
+  COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE,
+} = require("devtools/client/inspector/compatibility/actions/index");
+
+add_task(async function() {
+  const tab = await addTab("data:text/html;charset=utf-8,test");
+  const { inspector } = await openCompatibilityView();
+
+  let isFailureActionFired = false;
+  waitForDispatch(
+    inspector.store,
+    COMPATIBILITY_UPDATE_SELECTED_NODE_FAILURE
+  ).then(() => {
+    isFailureActionFired = true;
+  });
+
+  info("Reload the browsing page");
+  const onReloaded = BrowserTestUtils.browserLoaded(gBrowser.selectedBrowser);
+  const onUpdateAction = waitForUpdateSelectedNodeAction(inspector.store);
+  gBrowser.reloadTab(tab);
+  await Promise.all([onReloaded, onUpdateAction]);
+
+  info("Check whether the failure action will be fired or not");
+  ok(!isFailureActionFired, "No error occurred");
+});
diff --git a/devtools/client/inspector/compatibility/test/browser/head.js b/devtools/client/inspector/compatibility/test/browser/head.js
index fd28e5332f66..ac783ae9082d 100644
--- a/devtools/client/inspector/compatibility/test/browser/head.js
+++ b/devtools/client/inspector/compatibility/test/browser/head.js
@@ -11,6 +11,10 @@ Services.scriptloader.loadSubScript(
   this
 );
 
+const {
+  COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE,
+} = require("devtools/client/inspector/compatibility/actions/index");
+
 const {
   toCamelCase,
 } = require("devtools/client/inspector/compatibility/utils/cases");
@@ -20,6 +24,7 @@ async function openCompatibilityView() {
   await pushPref("devtools.inspector.compatibility.enabled", true);
 
   const { inspector } = await openInspectorSidebarTab("compatibilityview");
+  await waitForUpdateSelectedNodeAction(inspector.store);
   const panel = inspector.panelDoc.querySelector(
     "#compatibilityview-panel .inspector-tabpanel"
   );
@@ -66,3 +71,32 @@ async function assertIssueList(panel, expectedIssues) {
     }
   }
 }
+
+/**
+ * Return a promise which waits for COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE action.
+ *
+ * @param {Object} store
+ * @return {Promise}
+ */
+function waitForUpdateSelectedNodeAction(store) {
+  return waitForDispatch(store, COMPATIBILITY_UPDATE_SELECTED_NODE_COMPLETE);
+}
+
+/**
+ * Return a promise which waits for given action type.
+ *
+ * @param {Object} store
+ * @param {Object} type
+ * @return {Promise}
+ */
+function waitForDispatch(store, type) {
+  return new Promise(resolve => {
+    store.dispatch({
+      type: "@@service/waitUntil",
+      predicate: action => action.type === type,
+      run: (dispatch, getState, action) => {
+        resolve(action);
+      },
+    });
+  });
+}
diff --git a/dom/ipc/BrowserBridgeParent.cpp b/dom/ipc/BrowserBridgeParent.cpp
index f1754ea4eb11..e4c042ac3ab1 100644
--- a/dom/ipc/BrowserBridgeParent.cpp
+++ b/dom/ipc/BrowserBridgeParent.cpp
@@ -140,9 +140,7 @@ void BrowserBridgeParent::Destroy() {
 IPCResult BrowserBridgeParent::RecvShow(const ScreenIntSize& aSize,
                                         const bool& aParentIsActive,
                                         const nsSizeMode& aSizeMode) {
-  if (!mBrowserParent->AttachLayerManager()) {
-    MOZ_CRASH();
-  }
+  mBrowserParent->AttachLayerManager();
   Unused << mBrowserParent->SendShow(aSize, mBrowserParent->GetShowInfo(),
                                      aParentIsActive, aSizeMode);
   return IPC_OK();
diff --git a/gfx/wr/example-compositor/compositor-windows/src/lib.cpp b/gfx/wr/example-compositor/compositor-windows/src/lib.cpp
index fceedaf5a244..2c64aaeb2fd8 100644
--- a/gfx/wr/example-compositor/compositor-windows/src/lib.cpp
+++ b/gfx/wr/example-compositor/compositor-windows/src/lib.cpp
@@ -10,13 +10,18 @@
 #include <d3d11.h>
 #include <assert.h>
 #include <map>
+#include <vector>
 
 #define EGL_EGL_PROTOTYPES 1
 #define EGL_EGLEXT_PROTOTYPES 1
+#define GL_GLEXT_PROTOTYPES 1
 #include "EGL/egl.h"
 #include "EGL/eglext.h"
 #include "EGL/eglext_angle.h"
 #include "GL/gl.h"
+#include "GLES/gl.h"
+#include "GLES/glext.h"
+#include "GLES3/gl3.h"
 
 // The OS compositor representation of a picture cache tile.
 struct Tile {
@@ -26,6 +31,13 @@ struct Tile {
     IDCompositionVisual2 *pVisual;
 };
 
+struct CachedFrameBuffer {
+    int width;
+    int height;
+    GLuint fboId;
+    GLuint depthRboId;
+};
+
 struct Window {
     // Win32 window details
     HWND hWnd;
@@ -50,8 +62,9 @@ struct Window {
     EGLSurface fb_surface;
 
     // The currently bound surface, valid during bind() and unbind()
-    EGLSurface current_surface;
     IDCompositionSurface *pCurrentSurface;
+    EGLImage mEGLImage;
+    GLuint mColorRBO;
 
     // The root of the DC visual tree. Nothing is drawn on this, but
     // all child tiles are parented to here.
@@ -59,10 +72,50 @@ struct Window {
     IDCompositionVisualDebug *pVisualDebug;
     // Maps the WR surface IDs to the DC representation of each tile.
     std::map<uint64_t, Tile> tiles;
+    std::vector<CachedFrameBuffer> mFrameBuffers;
 };
 
 static const wchar_t *CLASS_NAME = L"WR DirectComposite";
 
+static GLuint GetOrCreateFbo(Window *window, int aWidth, int aHeight) {
+    GLuint fboId = 0;
+
+    // Check if we have a cached FBO with matching dimensions
+    for (auto it = window->mFrameBuffers.begin(); it != window->mFrameBuffers.end(); ++it) {
+        if (it->width == aWidth && it->height == aHeight) {
+            fboId = it->fboId;
+            break;
+        }
+    }
+
+    // If not, create a new FBO with attached depth buffer
+    if (fboId == 0) {
+        // Create the depth buffer
+        GLuint depthRboId;
+        glGenRenderbuffers(1, &depthRboId);
+        glBindRenderbuffer(GL_RENDERBUFFER, depthRboId);
+        glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT24,
+                              aWidth, aHeight);
+
+        // Create the framebuffer and attach the depth buffer to it
+        glGenFramebuffers(1, &fboId);
+        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboId);
+        glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER,
+                                  GL_DEPTH_ATTACHMENT,
+                                  GL_RENDERBUFFER, depthRboId);
+
+        // Store this in the cache for future calls.
+        CachedFrameBuffer frame_buffer_info;
+        frame_buffer_info.width = aWidth;
+        frame_buffer_info.height = aHeight;
+        frame_buffer_info.fboId = fboId;
+        frame_buffer_info.depthRboId = depthRboId;
+        window->mFrameBuffers.push_back(frame_buffer_info);
+    }
+
+    return fboId;
+}
+
 static LRESULT CALLBACK WndProc(
     HWND hwnd,
     UINT message,
@@ -86,6 +139,7 @@ extern "C" {
         window->width = width;
         window->height = height;
         window->enable_compositor = enable_compositor;
+        window->mEGLImage = EGL_NO_IMAGE;
 
         WNDCLASSEX wcex = { sizeof(WNDCLASSEX) };
         wcex.style = CS_HREDRAW | CS_VREDRAW;
@@ -284,7 +338,7 @@ extern "C" {
         delete window;
     }
 
-    bool com_dc_tick(Window *window) {
+    bool com_dc_tick(Window *) {
         // Check and dispatch the windows event loop
         MSG msg;
         while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE)) {
@@ -356,7 +410,7 @@ extern "C" {
     }
 
     // Bind a DC surface to allow issuing GL commands to it
-    void com_dc_bind_surface(
+    GLuint com_dc_bind_surface(
         Window *window,
         uint64_t id,
         int *x_offset,
@@ -395,35 +449,44 @@ extern "C" {
         offset.y -= dirty_y0;
         assert(SUCCEEDED(hr));
         pTexture->GetDesc(&desc);
-
-        // Construct an EGL off-screen surface that is bound to the DC surface
-        EGLint buffer_attribs[] = {
-            EGL_WIDTH, desc.Width,
-            EGL_HEIGHT, desc.Height,
-            EGL_FLEXIBLE_SURFACE_COMPATIBILITY_SUPPORTED_ANGLE, EGL_TRUE,
-            EGL_NONE
-        };
-
-        window->current_surface = eglCreatePbufferFromClientBuffer(
-            window->EGLDisplay,
-            EGL_D3D_TEXTURE_ANGLE,
-            pTexture,
-            window->config,
-            buffer_attribs
-        );
-        assert(window->current_surface != EGL_NO_SURFACE);
-
-        // Make EGL current on the DC surface
-        EGLBoolean ok = eglMakeCurrent(
-            window->EGLDisplay,
-            window->current_surface,
-            window->current_surface,
-            window->EGLContext
-        );
-        assert(ok);
-
         *x_offset = offset.x;
         *y_offset = offset.y;
+
+        // Construct an EGLImage wrapper around the D3D texture for ANGLE.
+        const EGLAttrib attribs[] = { EGL_NONE };
+        window->mEGLImage = eglCreateImage(
+            window->EGLDisplay,
+            EGL_NO_CONTEXT,
+            EGL_D3D11_TEXTURE_ANGLE,
+            static_cast<EGLClientBuffer>(pTexture),
+            attribs
+        );
+
+        // Get the current FBO and RBO id, so we can restore them later
+        GLint currentFboId, currentRboId;
+        glGetIntegerv(GL_DRAW_FRAMEBUFFER_BINDING, &currentFboId);
+        glGetIntegerv(GL_RENDERBUFFER_BINDING, &currentRboId);
+
+        // Create a render buffer object that is backed by the EGL image.
+        glGenRenderbuffers(1, &window->mColorRBO);
+        glBindRenderbuffer(GL_RENDERBUFFER, window->mColorRBO);
+        glEGLImageTargetRenderbufferStorageOES(GL_RENDERBUFFER, window->mEGLImage);
+
+        // Get or create an FBO for the specified dimensions
+        GLuint fboId = GetOrCreateFbo(window, desc.Width, desc.Height);
+
+        // Attach the new renderbuffer to the FBO
+        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, fboId);
+        glFramebufferRenderbuffer(GL_DRAW_FRAMEBUFFER,
+                                  GL_COLOR_ATTACHMENT0,
+                                  GL_RENDERBUFFER,
+                                  window->mColorRBO);
+
+        // Restore previous FBO and RBO bindings
+        glBindFramebuffer(GL_DRAW_FRAMEBUFFER, currentFboId);
+        glBindRenderbuffer(GL_RENDERBUFFER, currentRboId);
+
+        return fboId;
     }
 
     // Unbind a currently bound DC surface
@@ -431,7 +494,11 @@ extern "C" {
         HRESULT hr = window->pCurrentSurface->EndDraw();
         assert(SUCCEEDED(hr));
 
-        eglDestroySurface(window->EGLDisplay, window->current_surface);
+        glDeleteRenderbuffers(1, &window->mColorRBO);
+        window->mColorRBO = 0;
+
+        eglDestroyImage(window->EGLDisplay, window->mEGLImage);
+        window->mEGLImage = EGL_NO_IMAGE;
     }
 
     // At the start of a transaction, remove all visuals from the tree.
@@ -467,8 +534,8 @@ extern "C" {
 
         // Place the visual - this changes frame to frame based on scroll position
         // of the slice.
-        int offset_x = x + window->client_rect.left;
-        int offset_y = y + window->client_rect.top;
+        float offset_x = (float) (x + window->client_rect.left);
+        float offset_y = (float) (y + window->client_rect.top);
         tile.pVisual->SetOffsetX(offset_x);
         tile.pVisual->SetOffsetY(offset_y);
 
diff --git a/gfx/wr/example-compositor/compositor-windows/src/lib.rs b/gfx/wr/example-compositor/compositor-windows/src/lib.rs
index 4ccf780df5df..4362dd3eb481 100644
--- a/gfx/wr/example-compositor/compositor-windows/src/lib.rs
+++ b/gfx/wr/example-compositor/compositor-windows/src/lib.rs
@@ -50,7 +50,7 @@ extern {
         dirty_y0: i32,
         dirty_width: i32,
         dirty_height: i32,
-    );
+    ) -> u32;
     fn com_dc_unbind_surface(window: *mut Window);
 
     fn com_dc_begin_transaction(window: *mut Window);
@@ -130,12 +130,12 @@ pub fn bind_surface(
     dirty_y0: i32,
     dirty_width: i32,
     dirty_height: i32,
-) -> (i32, i32) {
+) -> (u32, i32, i32) {
     unsafe {
         let mut x_offset = 0;
         let mut y_offset = 0;
 
-        com_dc_bind_surface(
+        let fbo_id = com_dc_bind_surface(
             window,
             id,
             &mut x_offset,
@@ -146,7 +146,7 @@ pub fn bind_surface(
             dirty_height,
         );
 
-        (x_offset, y_offset)
+        (fbo_id, x_offset, y_offset)
     }
 }
 
diff --git a/gfx/wr/example-compositor/compositor/src/main.rs b/gfx/wr/example-compositor/compositor/src/main.rs
index bab9ac42aab1..e0393f9f3c6d 100644
--- a/gfx/wr/example-compositor/compositor/src/main.rs
+++ b/gfx/wr/example-compositor/compositor/src/main.rs
@@ -65,7 +65,7 @@ impl webrender::Compositor for DirectCompositeInterface {
         id: webrender::NativeSurfaceId,
         dirty_rect: DeviceIntRect,
     ) -> webrender::NativeSurfaceInfo {
-        let (x, y) = compositor::bind_surface(
+        let (fbo_id, x, y) = compositor::bind_surface(
             self.window,
             id.0,
             dirty_rect.origin.x,
@@ -76,7 +76,7 @@ impl webrender::Compositor for DirectCompositeInterface {
 
         webrender::NativeSurfaceInfo {
             origin: DeviceIntPoint::new(x, y),
-            fbo_id: 0,
+            fbo_id,
         }
     }
 
diff --git a/js/src/frontend/BinASTRuntimeSupport.h b/js/src/frontend/BinASTRuntimeSupport.h
index d6c333865830..695bafbbcc33 100644
--- a/js/src/frontend/BinASTRuntimeSupport.h
+++ b/js/src/frontend/BinASTRuntimeSupport.h
@@ -116,7 +116,13 @@ class BinASTSourceMetadata {
  public:
   BinASTSourceMetadata() = delete;
   explicit BinASTSourceMetadata(Type type) : type_(type) {}
+#ifdef JS_BUILD_BINAST
   ~BinASTSourceMetadata();
+#else
+  // If JS_BUILD_BINAST isn't defined, BinASTRuntimeSupport.cpp isn't built,
+  // but still the destructor is referred from ScriptSource::BinAST.
+  ~BinASTSourceMetadata() {}
+#endif  // JS_BUILD_BINAST
 
   Type type() const { return type_; }
 
diff --git a/js/src/shell/js.cpp b/js/src/shell/js.cpp
index 7fdce3420613..0fbdf71d6474 100644
--- a/js/src/shell/js.cpp
+++ b/js/src/shell/js.cpp
@@ -10981,7 +10981,7 @@ int main(int argc, char** argv, char** envp) {
                           "Format of BinAST file (multipart/context)") ||
 #else
       !op.addMultiStringOption('B', "binast", "", "No-op") ||
-      !op.addStringOption('\0', "binast-format", "No-op") ||
+      !op.addStringOption('\0', "binast-format", "[format]", "No-op") ||
 #endif  // JS_BUILD_BINAST
       !op.addMultiStringOption('e', "execute", "CODE", "Inline code to run") ||
       !op.addBoolOption('i', "shell", "Enter prompt after running code") ||
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index c52a95d71c20..fa71c3d4e359 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -4151,6 +4151,12 @@
   value: false
   mirror: always
 
+# Whether we allow advanced layers with fission
+- name: layers.advanced.fission.enabled
+  type: bool
+  value: false
+  mirror: always
+
 # Whether we allow AMD switchable graphics.
 - name: layers.amd-switchable-gfx.enabled
   type: bool
diff --git a/parser/html/nsHtml5TreeOpExecutor.cpp b/parser/html/nsHtml5TreeOpExecutor.cpp
index f2588d3b6514..1ce3100019c9 100644
--- a/parser/html/nsHtml5TreeOpExecutor.cpp
+++ b/parser/html/nsHtml5TreeOpExecutor.cpp
@@ -450,6 +450,16 @@ void nsHtml5TreeOpExecutor::RunFlushLoop() {
       // Now parse content left in the document.write() buffer queue if any.
       // This may generate tree ops on its own or dequeue a speculation.
       nsresult rv = GetParser()->ParseUntilBlocked();
+
+      // ParseUntilBlocked flushes operations from the stage to the OpQueue.
+      // Those operations may have accompanying speculative operations.
+      // If so, we have to flush those speculative loads so that we maintain
+      // the invariant that no speculative load starts after the corresponding
+      // normal load for the same URL. See
+      // https://bugzilla.mozilla.org/show_bug.cgi?id=1513292#c80
+      // for a more detailed explanation of why this is necessary.
+      FlushSpeculativeLoads();
+
       if (NS_FAILED(rv)) {
         MarkAsBroken(rv);
         return;
diff --git a/services/fxaccounts/FxAccounts.jsm b/services/fxaccounts/FxAccounts.jsm
index 61b39d665823..13c1842679a1 100644
--- a/services/fxaccounts/FxAccounts.jsm
+++ b/services/fxaccounts/FxAccounts.jsm
@@ -874,7 +874,7 @@ FxAccountsInternal.prototype = {
   _telemetry: null,
   get telemetry() {
     if (!this._telemetry) {
-      this._telemetry = new FxAccountsTelemetry();
+      this._telemetry = new FxAccountsTelemetry(this);
     }
     return this._telemetry;
   },
diff --git a/services/fxaccounts/FxAccountsTelemetry.jsm b/services/fxaccounts/FxAccountsTelemetry.jsm
index 8f1dadedd7fa..5e445da74e0c 100644
--- a/services/fxaccounts/FxAccountsTelemetry.jsm
+++ b/services/fxaccounts/FxAccountsTelemetry.jsm
@@ -9,13 +9,25 @@
 // sanely shared (eg, services-common?), but let's wait and see where we end up
 // first...
 
-// We use this observers module because we leverage its support for richer
-// "subject" data.
-const { Observers } = ChromeUtils.import(
-  "resource://services-common/observers.js"
+const { XPCOMUtils } = ChromeUtils.import(
+  "resource://gre/modules/XPCOMUtils.jsm"
 );
 
+XPCOMUtils.defineLazyModuleGetters(this, {
+  log: "resource://gre/modules/FxAccountsCommon.js",
+  // We use this observers module because we leverage its support for richer
+  // "subject" data.
+  Observers: "resource://services-common/observers.js",
+  Services: "resource://gre/modules/Services.jsm",
+});
+
 class FxAccountsTelemetry {
+  constructor(fxai) {
+    this._fxai = fxai;
+    Services.telemetry.setEventRecordingEnabled("fxa", true);
+  }
+
+  // Records an event *in the Fxa/Sync ping*.
   recordEvent(object, method, value, extra = undefined) {
     // We need to ensure the telemetry module is loaded.
     ChromeUtils.import("resource://services-sync/telemetry.js");
@@ -50,6 +62,81 @@ class FxAccountsTelemetry {
     }
     return null;
   }
+
+  // Record the connection of FxA or one of its services.
+  // Note that you must call this before performing the actual connection
+  // or we may record incorrect data - for example, we will not be able to
+  // determine whether FxA itself was connected before this call.
+  //
+  // Currently sends an event in the main telemetry event ping rather than the
+  // FxA/Sync ping (although this might change in the future)
+  //
+  // @param services - An array of service names which should be recorded. FxA
+  //  itself is not counted as a "service" - ie, an empty array should be passed
+  //  if the account is connected without anything else .
+  //
+  // @param how - How the connection was done.
+  async recordConnection(services, how = null) {
+    try {
+      let extra = {};
+      // Record that fxa was connected if it isn't currently - it will be soon.
+      if (!(await this._fxai.getUserAccountData())) {
+        extra.fxa = "true";
+      }
+      // Events.yaml only declares "sync" as a valid service.
+      if (services.includes("sync")) {
+        extra.sync = "true";
+      }
+      Services.telemetry.recordEvent("fxa", "connect", "account", how, extra);
+    } catch (ex) {
+      log.error("Failed to record connection telemetry", ex);
+      console.error("Failed to record connection telemetry", ex);
+    }
+  }
+
+  // Record the disconnection of FxA or one of its services.
+  // Note that you must call this before performing the actual disconnection
+  // or we may record incomplete data - for example, if this is called after
+  // disconnection, we've almost certainly lost the ability to record what
+  // services were enabled prior to disconnection.
+  //
+  // Currently sends an event in the main telemetry event ping rather than the
+  // FxA/Sync ping (although this might change in the future)
+  //
+  // @param service - the service being disconnected. If null, the account
+  // itself is being disconnected, so all connected services are too.
+  //
+  // @param how - how the disconnection was done.
+  async recordDisconnection(service = null, how = null) {
+    try {
+      let extra = {};
+      if (!service) {
+        extra.fxa = "true";
+        // We need a way to enumerate all services - but for now we just hard-code
+        // all possibilities here.
+        if (Services.prefs.prefHasUserValue("services.sync.username")) {
+          extra.sync = "true";
+        }
+      } else if (service == "sync") {
+        extra[service] = "true";
+      } else {
+        // Events.yaml only declares "sync" as a valid service.
+        log.warn(
+          `recordDisconnection has invalid value for service: ${service}`
+        );
+      }
+      Services.telemetry.recordEvent(
+        "fxa",
+        "disconnect",
+        "account",
+        how,
+        extra
+      );
+    } catch (ex) {
+      log.error("Failed to record disconnection telemetry", ex);
+      console.error("Failed to record disconnection telemetry", ex);
+    }
+  }
 }
 
 var EXPORTED_SYMBOLS = ["FxAccountsTelemetry"];
diff --git a/services/fxaccounts/FxAccountsWebChannel.jsm b/services/fxaccounts/FxAccountsWebChannel.jsm
index 5c365a6c4045..ccae44dd9f39 100644
--- a/services/fxaccounts/FxAccountsWebChannel.jsm
+++ b/services/fxaccounts/FxAccountsWebChannel.jsm
@@ -434,6 +434,11 @@ this.FxAccountsWebChannelHelpers.prototype = {
     // Remember who it was so we can log out next time.
     this.setPreviousAccountNameHashPref(accountData.email);
 
+    await this._fxAccounts.telemetry.recordConnection(
+      Object.keys(requestedServices || {}),
+      "webchannel"
+    );
+
     // A sync-specific hack - we want to ensure sync has been initialized
     // before we set the signed-in user.
     // XXX - probably not true any more, especially now we have observerPreloads
@@ -479,17 +484,15 @@ this.FxAccountsWebChannelHelpers.prototype = {
    *
    * @param the uid of the account which have been logged out
    */
-  logout(uid) {
-    return this._fxAccounts._internal
-      .getUserAccountData(["uid"])
-      .then(userData => {
-        if (userData && userData.uid === uid) {
-          // true argument is `localOnly`, because server-side stuff
-          // has already been taken care of by the content server
-          return fxAccounts.signOut(true);
-        }
-        return null;
-      });
+  async logout(uid) {
+    let fxa = this._fxAccounts;
+    let userData = await fxa._internal.getUserAccountData(["uid"]);
+    if (userData && userData.uid === uid) {
+      await fxa.telemetry.recordDisconnection(null, "webchannel");
+      // true argument is `localOnly`, because server-side stuff
+      // has already been taken care of by the content server
+      await fxa.signOut(true);
+    }
   },
 
   /**
diff --git a/services/fxaccounts/tests/xpcshell/test_web_channel.js b/services/fxaccounts/tests/xpcshell/test_web_channel.js
index c66cac22dbde..6f3917ed55bf 100644
--- a/services/fxaccounts/tests/xpcshell/test_web_channel.js
+++ b/services/fxaccounts/tests/xpcshell/test_web_channel.js
@@ -396,6 +396,9 @@ add_task(async function test_helpers_login_without_customize_sync() {
           });
         },
       },
+      telemetry: {
+        recordConnection: sinon.spy(),
+      },
     },
     weaveXPCOM: {
       whenLoaded() {},
@@ -415,6 +418,9 @@ add_task(async function test_helpers_login_without_customize_sync() {
     verifiedCanLinkAccount: true,
     customizeSync: false,
   });
+  Assert.ok(
+    helpers._fxAccounts.telemetry.recordConnection.calledWith([], "webchannel")
+  );
 });
 
 add_task(async function test_helpers_login_with_customize_sync() {
@@ -433,6 +439,9 @@ add_task(async function test_helpers_login_with_customize_sync() {
           });
         },
       },
+      telemetry: {
+        recordConnection: sinon.spy(),
+      },
     },
     weaveXPCOM: {
       whenLoaded() {},
@@ -449,6 +458,9 @@ add_task(async function test_helpers_login_with_customize_sync() {
     verifiedCanLinkAccount: true,
     customizeSync: true,
   });
+  Assert.ok(
+    helpers._fxAccounts.telemetry.recordConnection.calledWith([], "webchannel")
+  );
 });
 
 add_task(
@@ -469,6 +481,9 @@ add_task(
             });
           },
         },
+        telemetry: {
+          recordConnection: sinon.spy(),
+        },
       },
       weaveXPCOM: {
         whenLoaded() {},
@@ -542,6 +557,12 @@ add_task(
     );
     Assert.equal(Services.prefs.getBoolPref("services.sync.engine.tabs"), true);
     Assert.ok(configured, "sync was configured");
+    Assert.ok(
+      helpers._fxAccounts.telemetry.recordConnection.calledWith(
+        ["sync"],
+        "webchannel"
+      )
+    );
   }
 );
 
@@ -556,6 +577,9 @@ add_task(async function test_helpers_login_with_offered_sync_engines() {
             resolve(accountData);
           },
         },
+        telemetry: {
+          recordConnection() {},
+        },
       },
       weaveXPCOM: {
         whenLoaded() {},
@@ -610,6 +634,9 @@ add_task(async function test_helpers_login_nothing_offered() {
             resolve(accountData);
           },
         },
+        telemetry: {
+          recordConnection() {},
+        },
       },
       weaveXPCOM: {
         whenLoaded() {},
diff --git a/testing/web-platform/tests/css/css-grid/parsing/grid-area-valid.html b/testing/web-platform/tests/css/css-grid/parsing/grid-area-valid.html
index abe58951efeb..9f93e6325b1b 100644
--- a/testing/web-platform/tests/css/css-grid/parsing/grid-area-valid.html
+++ b/testing/web-platform/tests/css/css-grid/parsing/grid-area-valid.html
@@ -76,11 +76,12 @@ test_valid_value("grid-row", "2 i / auto", "2 i");
 test_valid_value("grid-row", "1 / auto", "1");
 test_valid_value("grid-column", "2 j / span 3 k");
 
-
 // https://github.com/w3c/csswg-drafts/issues/2858
-// '\\31 st' in Blink, Firefox, '1st' in Edge, '"1st"' in Safari.
-test_valid_value("grid-column-end",  "\\31st", ["\\31 st", "1st", '"1st"']);
-test_valid_value("grid-column-end",  "\\31 st", ["\\31 st", "1st", '"1st"']);
+// '\\31 st' in Blink, Firefox, EdgeHTML and Safari serialize invalid values.
+test_valid_value("grid-column-end", "\\31st", ["\\31 st", "\\31st"]);
+test_valid_value("grid-column-end", "\\31 st", ["\\31 st", "\\31st"]);
+test_valid_value("grid-column", "\\31st / \\31 st", ["\\31 st", "\\31st"]);
+
 </script>
 </body>
 </html>
diff --git a/toolkit/components/telemetry/Events.yaml b/toolkit/components/telemetry/Events.yaml
index 03803ffbd43d..60df034cdd7c 100644
--- a/toolkit/components/telemetry/Events.yaml
+++ b/toolkit/components/telemetry/Events.yaml
@@ -656,6 +656,26 @@ pwmgr:
     release_channel_collection: opt-out
     expiry_version: never
 
+fxa:
+  connect:
+    objects: ["account"]
+    methods: ["connect", "disconnect"]
+    description: >
+      Records when a Firefox Account, or a Firefox Account service, is explicitly
+      connected or disconnected from the browser via an intentional user action.
+    extra_keys:
+      fxa: Whether the account itself was connected or disconnected.
+      sync: Whether sync was connected or disconnected.
+    products:
+      - "firefox"
+      - "fennec"
+      - "geckoview"
+    record_in_processes: ["main"]
+    bug_numbers: [1595954]
+    notification_emails: ["sync-dev@mozilla.org"]
+    release_channel_collection: opt-out
+    expiry_version: never
+
 fxa_avatar_menu:
   click:
     objects: [
diff --git a/widget/nsBaseWidget.cpp b/widget/nsBaseWidget.cpp
index 4ed9df6cc2cd..1cd861843258 100644
--- a/widget/nsBaseWidget.cpp
+++ b/widget/nsBaseWidget.cpp
@@ -54,6 +54,7 @@
 #include "mozilla/StaticPrefs_apz.h"
 #include "mozilla/StaticPrefs_dom.h"
 #include "mozilla/StaticPrefs_layout.h"
+#include "mozilla/StaticPrefs_layers.h"
 #include "mozilla/Unused.h"
 #include "mozilla/IMEStateManager.h"
 #include "mozilla/VsyncDispatcher.h"
@@ -72,7 +73,6 @@
 #include "mozilla/gfx/gfxVars.h"
 #include "mozilla/Move.h"
 #include "mozilla/Sprintf.h"
-#include "mozilla/StaticPrefs_layout.h"
 #include "mozilla/webrender/WebRenderTypes.h"
 #include "nsRefPtrHashtable.h"
 #include "TouchEvents.h"
@@ -172,6 +172,7 @@ nsBaseWidget::nsBaseWidget()
       mPopupLevel(ePopupLevelTop),
       mPopupType(ePopupTypeAny),
       mHasRemoteContent(false),
+      mFissionWindow(false),
       mUpdateCursor(true),
       mUseAttachedEvents(false),
       mIMEHasFocus(false),
@@ -391,6 +392,7 @@ void nsBaseWidget::BaseCreate(nsIWidget* aParent, nsWidgetInitData* aInitData) {
     mPopupLevel = aInitData->mPopupLevel;
     mPopupType = aInitData->mPopupHint;
     mHasRemoteContent = aInitData->mHasRemoteContent;
+    mFissionWindow = aInitData->mFissionWindow;
   }
 
   if (aParent) {
@@ -1213,7 +1215,11 @@ already_AddRefed<LayerManager> nsBaseWidget::CreateCompositorSession(
     bool enableAPZ = UseAPZ();
     CompositorOptions options(enableAPZ, enableWR);
 
-    bool enableAL = gfx::gfxConfig::IsEnabled(gfx::Feature::ADVANCED_LAYERS);
+    // Bug 1588484 - Advanced Layers is currently disabled for fission windows,
+    // since it doesn't properly support nested RefLayers.
+    bool enableAL =
+        gfx::gfxConfig::IsEnabled(gfx::Feature::ADVANCED_LAYERS) &&
+        (!mFissionWindow || StaticPrefs::layers_advanced_fission_enabled());
     options.SetUseAdvancedLayers(enableAL);
 
 #ifdef MOZ_WIDGET_ANDROID
diff --git a/widget/nsBaseWidget.h b/widget/nsBaseWidget.h
index 02e6470539ac..9ebfde22bbcb 100644
--- a/widget/nsBaseWidget.h
+++ b/widget/nsBaseWidget.h
@@ -691,6 +691,7 @@ class nsBaseWidget : public nsIWidget, public nsSupportsWeakReference {
   nsPopupType mPopupType;
   SizeConstraints mSizeConstraints;
   bool mHasRemoteContent;
+  bool mFissionWindow;
 
   bool mUpdateCursor;
   bool mUseAttachedEvents;
diff --git a/widget/nsWidgetInitData.h b/widget/nsWidgetInitData.h
index e40199cfb807..37bb2ab2b50b 100644
--- a/widget/nsWidgetInitData.h
+++ b/widget/nsWidgetInitData.h
@@ -112,7 +112,8 @@ struct nsWidgetInitData {
         mMouseTransparent(false),
         mHasRemoteContent(false),
         mAlwaysOnTop(false),
-        mPIPWindow(false) {}
+        mPIPWindow(false),
+        mFissionWindow(false) {}
 
   nsWindowType mWindowType;
   nsBorderStyle mBorderStyle;
@@ -140,6 +141,8 @@ struct nsWidgetInitData {
   bool mAlwaysOnTop;
   // Is PictureInPicture window
   bool mPIPWindow;
+  // True if fission is enabled for this window
+  bool mFissionWindow;
 };
 
 #endif  // nsWidgetInitData_h__
diff --git a/xpfe/appshell/nsAppShellService.cpp b/xpfe/appshell/nsAppShellService.cpp
index 9dbb20e1cb45..137c8ffe247e 100644
--- a/xpfe/appshell/nsAppShellService.cpp
+++ b/xpfe/appshell/nsAppShellService.cpp
@@ -593,6 +593,9 @@ nsresult nsAppShellService::JustCreateTopWindow(
   if (aChromeMask & nsIWebBrowserChrome::CHROME_ALWAYS_ON_TOP)
     widgetInitData.mAlwaysOnTop = true;
 
+  if (aChromeMask & nsIWebBrowserChrome::CHROME_FISSION_WINDOW)
+    widgetInitData.mFissionWindow = true;
+
 #ifdef MOZ_WIDGET_GTK
   // Linux/Gtk PIP window support. It's Chrome Toplevel window, always on top
   // and without any bar.