diff --git a/browser/components/enterprisepolicies/tests/browser/browser_policy_set_homepage.js b/browser/components/enterprisepolicies/tests/browser/browser_policy_set_homepage.js
index 8cde3b850cb2..0fa6a948c0b6 100644
--- a/browser/components/enterprisepolicies/tests/browser/browser_policy_set_homepage.js
+++ b/browser/components/enterprisepolicies/tests/browser/browser_policy_set_homepage.js
@@ -45,7 +45,7 @@ async function check_homepage({expectedURL, expectedPageVal = -1, locked = false
       // If only StartPage was changed, no need to check these
       return;
     }
-    content.document.getElementById("category-home").click();
+    await content.gotoPref("paneHome");
 
     let homepageTextbox = content.document.getElementById("homePageUrl");
     // Unfortunately this test does not work because the new UI does not fill
diff --git a/browser/components/preferences/in-content/findInPage.js b/browser/components/preferences/in-content/findInPage.js
index af27d75fbf16..5ae0370273d5 100644
--- a/browser/components/preferences/in-content/findInPage.js
+++ b/browser/components/preferences/in-content/findInPage.js
@@ -35,9 +35,9 @@ var gSearchResultsPane = {
     helpContainer.querySelector("a").href = helpUrl;
   },
 
-  handleEvent(event) {
+  async handleEvent(event) {
     // Ensure categories are initialized if idle callback didn't run sooo enough.
-    this.initializeCategories();
+    await this.initializeCategories();
     this.searchFunction(event);
   },
 
@@ -63,14 +63,14 @@ var gSearchResultsPane = {
   /**
    * Will attempt to initialize all uninitialized categories
    */
-  initializeCategories() {
+  async initializeCategories() {
     //  Initializing all the JS for all the tabs
     if (!this.categoriesInitialized) {
       this.categoriesInitialized = true;
       // Each element of gCategoryInits is a name
       for (let [/* name */, category] of gCategoryInits) {
         if (!category.inited) {
-          category.init();
+          await category.init();
         }
       }
     }
@@ -223,10 +223,10 @@ var gSearchResultsPane = {
 
     let srHeader = document.getElementById("header-searchResults");
     let noResultsEl = document.getElementById("no-results-message");
-    srHeader.hidden = !this.query;
     if (this.query) {
       // Showing the Search Results Tag
-      gotoPref("paneSearchResults");
+      await gotoPref("paneSearchResults");
+      srHeader.hidden = false;
 
       let resultsFound = false;
 
@@ -307,7 +307,8 @@ var gSearchResultsPane = {
       noResultsEl.hidden = true;
       document.getElementById("sorry-message-query").textContent = "";
       // Going back to General when cleared
-      gotoPref("paneGeneral");
+      await gotoPref("paneGeneral");
+      srHeader.hidden = true;
 
       // Hide some special second level headers in normal view
       for (let element of document.querySelectorAll(".search-header")) {
diff --git a/browser/components/preferences/in-content/preferences.js b/browser/components/preferences/in-content/preferences.js
index c04e67655f57..5d7077b5aebf 100644
--- a/browser/components/preferences/in-content/preferences.js
+++ b/browser/components/preferences/in-content/preferences.js
@@ -24,7 +24,7 @@ ChromeUtils.defineModuleGetter(this, "AMTelemetry",
 ChromeUtils.defineModuleGetter(this, "formAutofillParent",
                                "resource://formautofill/FormAutofillParent.jsm");
 
-var gLastHash = "";
+var gLastCategory = {category: undefined, subcategory: undefined};
 const gXULDOMParser = new DOMParser();
 
 var gCategoryInits = new Map();
@@ -34,48 +34,27 @@ function init_category_if_required(category) {
     throw "Unknown in-content prefs category! Can't init " + category;
   }
   if (categoryInfo.inited) {
-    return;
+    return null;
   }
-  categoryInfo.init();
+  return categoryInfo.init();
 }
 
 function register_module(categoryName, categoryObject) {
   gCategoryInits.set(categoryName, {
     inited: false,
-    init() {
+    async init() {
       let template = document.getElementById("template-" + categoryName);
       if (template) {
         // Replace the template element with the nodes from the parsed comment
         // string.
         let frag = MozXULElement.parseXULToFragment(template.firstChild.data);
 
-        // Gather the to-be-translated elements so that we could pass them to
-        // l10n.translateElements() and get a translated promise.
-        // Here we loop through the first level elements (<hbox>/<groupbox>/<deck>/etc)
-        // because we know that they are not implemented by XBL bindings,
-        // so it's ok to get a reference of them before inserting the node
-        // to the DOM.
-        //
-        // If we don't have to worry about XBL, this can simply be
-        // let l10nUpdatedElements = Array.from(frag.querySelectorAll("[data-l10n-id]"))
-        //
-        // If we can get a translated promise after insertion, this can all be
-        // removed (see bug 1520659.)
-        let firstLevelElements = Array.from(frag.children);
+        await document.l10n.translateFragment(frag);
 
         // Actually insert them into the DOM.
+        document.l10n.pauseObserving();
         template.replaceWith(frag);
-
-        let l10nUpdatedElements = [];
-        // Collect the elements from the newly inserted first level elements.
-        for (let el of firstLevelElements) {
-          l10nUpdatedElements = l10nUpdatedElements.concat(
-            Array.from(el.querySelectorAll("[data-l10n-id]")));
-        }
-
-        // Set a promise on the categoryInfo object that the highlight code can await on.
-        this.translated = document.l10n.translateElements(l10nUpdatedElements)
-          .then(() => this.translated = undefined);
+        document.l10n.resumeObserving();
 
         // Asks Preferences to update the attribute value of the entire
         // document again (this can be simplified if we could seperate the
@@ -122,26 +101,27 @@ function init_all() {
   maybeDisplayPoliciesNotice();
 
   window.addEventListener("hashchange", onHashChange);
-  gotoPref();
 
-  let helpButton = document.getElementById("helpButton");
-  let helpUrl = Services.urlFormatter.formatURLPref("app.support.baseURL") + "preferences";
-  helpButton.setAttribute("href", helpUrl);
+  gotoPref().then(() => {
+    let helpButton = document.getElementById("helpButton");
+    let helpUrl = Services.urlFormatter.formatURLPref("app.support.baseURL") + "preferences";
+    helpButton.setAttribute("href", helpUrl);
 
-  document.getElementById("addonsButton")
-    .addEventListener("click", () => {
-      let mainWindow = window.docShell.rootTreeItem.domWindow;
-      mainWindow.BrowserOpenAddonsMgr();
-      AMTelemetry.recordLinkEvent({
-        object: "aboutPreferences",
-        value: "about:addons",
+    document.getElementById("addonsButton")
+      .addEventListener("click", () => {
+        let mainWindow = window.docShell.rootTreeItem.domWindow;
+        mainWindow.BrowserOpenAddonsMgr();
+        AMTelemetry.recordLinkEvent({
+          object: "aboutPreferences",
+          value: "about:addons",
+        });
       });
-    });
 
-  document.dispatchEvent(new CustomEvent("Initialized", {
-    "bubbles": true,
-    "cancelable": true,
-  }));
+    document.dispatchEvent(new CustomEvent("Initialized", {
+      "bubbles": true,
+      "cancelable": true,
+    }));
+  });
 }
 
 function telemetryBucketForCategory(category) {
@@ -164,7 +144,7 @@ function onHashChange() {
   gotoPref();
 }
 
-function gotoPref(aCategory) {
+async function gotoPref(aCategory) {
   let categories = document.getElementById("categories");
   const kDefaultCategoryInternalName = "paneGeneral";
   const kDefaultCategory = "general";
@@ -195,7 +175,7 @@ function gotoPref(aCategory) {
 
   // Updating the hash (below) or changing the selected category
   // will re-enter gotoPref.
-  if (gLastHash == category && !subcategory)
+  if (gLastCategory.category == category && !subcategory)
     return;
 
   let item;
@@ -207,26 +187,35 @@ function gotoPref(aCategory) {
     }
   }
 
-  try {
-    init_category_if_required(category);
-  } catch (ex) {
-    Cu.reportError("Error initializing preference category " + category + ": " + ex);
-    throw ex;
-  }
-
-  let friendlyName = internalPrefCategoryNameToFriendlyName(category);
-  if (gLastHash || category != kDefaultCategoryInternalName || subcategory) {
+  if (gLastCategory.category || category != kDefaultCategoryInternalName || subcategory) {
+    let friendlyName = internalPrefCategoryNameToFriendlyName(category);
     document.location.hash = friendlyName;
   }
-  // Need to set the gLastHash before setting categories.selectedItem since
+  // Need to set the gLastCategory before setting categories.selectedItem since
   // the categories 'select' event will re-enter the gotoPref codepath.
-  gLastHash = category;
+  gLastCategory.category = category;
+  gLastCategory.subcategory = subcategory;
   if (item) {
     categories.selectedItem = item;
   } else {
     categories.clearSelection();
   }
   window.history.replaceState(category, document.title);
+
+  try {
+    await init_category_if_required(category);
+  } catch (ex) {
+    Cu.reportError(new Error("Error initializing preference category " + category + ": " + ex));
+    throw ex;
+  }
+
+  // Bail out of this goToPref if the category
+  // or subcategory changed during async operation.
+  if (gLastCategory.category !== category ||
+      gLastCategory.subcategory !== subcategory) {
+    return;
+  }
+
   search(category, "data-category");
 
   let mainContent = document.querySelector(".main-content");
@@ -284,7 +273,6 @@ async function scrollAndHighlight(subcategory, category) {
     return;
   }
   let header = getClosestDisplayedHeader(element);
-  await gCategoryInits.get(category).translated;
 
   scrollContentTo(header);
   element.classList.add("spotlight");
diff --git a/browser/components/preferences/in-content/tests/browser_bug1018066_resetScrollPosition.js b/browser/components/preferences/in-content/tests/browser_bug1018066_resetScrollPosition.js
index 7487e55e648d..312790504a61 100644
--- a/browser/components/preferences/in-content/tests/browser_bug1018066_resetScrollPosition.js
+++ b/browser/components/preferences/in-content/tests/browser_bug1018066_resetScrollPosition.js
@@ -17,7 +17,8 @@ add_task(async function() {
   mainContent.scrollTop = 50;
   is(mainContent.scrollTop, 50, "main-content should be scrolled 50 pixels");
 
-  gBrowser.contentWindow.gotoPref("paneGeneral");
+  await gBrowser.contentWindow.gotoPref("paneGeneral");
+
   is(mainContent.scrollTop, 0,
      "Switching to a different category should reset the scroll position");
 });
diff --git a/browser/components/preferences/in-content/tests/browser_bug731866.js b/browser/components/preferences/in-content/tests/browser_bug731866.js
index f095027178f0..c719c7aab8bf 100644
--- a/browser/components/preferences/in-content/tests/browser_bug731866.js
+++ b/browser/components/preferences/in-content/tests/browser_bug731866.js
@@ -35,7 +35,7 @@ function checkElements(expectedPane) {
   }
 }
 
-function runTest(win) {
+async function runTest(win) {
   is(gBrowser.currentURI.spec, "about:preferences", "about:preferences loaded");
 
   let tab = win.document;
@@ -47,7 +47,7 @@ function runTest(win) {
   ];
 
   for (let pane of panes) {
-    win.gotoPref("pane" + pane);
+    await win.gotoPref("pane" + pane);
     checkElements(pane);
   }
 
diff --git a/browser/components/preferences/in-content/tests/browser_bug795764_cachedisabled.js b/browser/components/preferences/in-content/tests/browser_bug795764_cachedisabled.js
index f8f67983f6c0..6e4808545907 100644
--- a/browser/components/preferences/in-content/tests/browser_bug795764_cachedisabled.js
+++ b/browser/components/preferences/in-content/tests/browser_bug795764_cachedisabled.js
@@ -17,14 +17,14 @@ function test() {
   ]}).then(() => open_preferences(runTest));
 }
 
-function runTest(win) {
+async function runTest(win) {
   is(gBrowser.currentURI.spec, "about:preferences", "about:preferences loaded");
 
   let tab = win.document;
   let elements = tab.getElementById("mainPrefPane").children;
 
   // Test if privacy pane is opened correctly
-  win.gotoPref("panePrivacy");
+  await win.gotoPref("panePrivacy");
   for (let element of elements) {
     let attributeValue = element.getAttribute("data-category");
     if (attributeValue == "panePrivacy") {
diff --git a/browser/components/preferences/in-content/tests/browser_healthreport.js b/browser/components/preferences/in-content/tests/browser_healthreport.js
index bbfae9707c37..8d2afe9b06db 100644
--- a/browser/components/preferences/in-content/tests/browser_healthreport.js
+++ b/browser/components/preferences/in-content/tests/browser_healthreport.js
@@ -6,9 +6,9 @@
 const FHR_UPLOAD_ENABLED = "datareporting.healthreport.uploadEnabled";
 
 function runPaneTest(fn) {
-  open_preferences((win) => {
+  open_preferences(async (win) => {
     let doc = win.document;
-    win.gotoPref("paneAdvanced");
+    await win.gotoPref("paneAdvanced");
     let advancedPrefs = doc.getElementById("advancedPrefs");
     let tab = doc.getElementById("dataChoicesTab");
     advancedPrefs.selectedTab = tab;
diff --git a/browser/components/preferences/in-content/tests/browser_search_no_results_change_category.js b/browser/components/preferences/in-content/tests/browser_search_no_results_change_category.js
index d01cb98a3b3d..e0d8c850bece 100644
--- a/browser/components/preferences/in-content/tests/browser_search_no_results_change_category.js
+++ b/browser/components/preferences/in-content/tests/browser_search_no_results_change_category.js
@@ -19,8 +19,7 @@ add_task(async function() {
   let noResultsEl = gBrowser.contentDocument.querySelector("#no-results-message");
   is_element_visible(noResultsEl, "Should be reporting no results for this query");
 
-  let privacyCategory = gBrowser.contentDocument.querySelector("#category-privacy");
-  privacyCategory.click();
+  await gBrowser.contentWindow.gotoPref("panePrivacy");
   is_element_hidden(noResultsEl,
                     "Should not be showing the 'no results' message after selecting a category");
 
diff --git a/browser/components/preferences/in-content/tests/browser_telemetry.js b/browser/components/preferences/in-content/tests/browser_telemetry.js
index d8139d87af45..b06f65896a86 100644
--- a/browser/components/preferences/in-content/tests/browser_telemetry.js
+++ b/browser/components/preferences/in-content/tests/browser_telemetry.js
@@ -6,9 +6,9 @@
 const PREF_TELEMETRY_ENABLED = "toolkit.telemetry.enabled";
 
 function runPaneTest(fn) {
-  open_preferences((win) => {
+  open_preferences(async (win) => {
     let doc = win.document;
-    win.gotoPref("paneAdvanced");
+    await win.gotoPref("paneAdvanced");
     let advancedPrefs = doc.getElementById("advancedPrefs");
     let tab = doc.getElementById("dataChoicesTab");
     advancedPrefs.selectedTab = tab;
diff --git a/browser/components/preferences/in-content/tests/privacypane_tests_perwindow.js b/browser/components/preferences/in-content/tests/privacypane_tests_perwindow.js
index 0edea84cc9a9..1e5f223b3241 100644
--- a/browser/components/preferences/in-content/tests/privacypane_tests_perwindow.js
+++ b/browser/components/preferences/in-content/tests/privacypane_tests_perwindow.js
@@ -6,7 +6,7 @@ async function runTestOnPrivacyPrefPane(testFunc) {
   let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, "about:preferences", true, true);
   let browser = tab.linkedBrowser;
   info("loaded about:preferences");
-  browser.contentWindow.gotoPref("panePrivacy");
+  await browser.contentWindow.gotoPref("panePrivacy");
   info("viewing privacy pane, executing testFunc");
   await testFunc(browser.contentWindow);
   BrowserTestUtils.removeTab(tab);
diff --git a/dom/webidl/DocumentL10n.webidl b/dom/webidl/DocumentL10n.webidl
index 657a63722c97..9a6090d9ba69 100644
--- a/dom/webidl/DocumentL10n.webidl
+++ b/dom/webidl/DocumentL10n.webidl
@@ -141,6 +141,18 @@ interface DocumentL10n {
    */
   [NewObject] Promise<void> translateElements(sequence<Element> aElements);
 
+  /**
+   * Pauses the MutationObserver set to observe
+   * localization related DOM mutations.
+   */
+  [Throws] void pauseObserving();
+
+  /**
+   * Resumes the MutationObserver set to observe
+   * localization related DOM mutations.
+   */
+  [Throws] void resumeObserving();
+
   /**
    * A promise which gets resolved when the initial DOM localization resources
    * fetching is complete and the initial translation of the DOM is finished.
diff --git a/intl/l10n/DOMLocalization.jsm b/intl/l10n/DOMLocalization.jsm
index 2b0bec5ea5d6..7cba3c71ffd4 100644
--- a/intl/l10n/DOMLocalization.jsm
+++ b/intl/l10n/DOMLocalization.jsm
@@ -510,6 +510,13 @@ class DOMLocalization extends Localization {
    * @param {Element}      newRoot - Root to observe.
    */
   connectRoot(newRoot) {
+    // Sometimes we connect the root while the document is already in the
+    // process of being closed. Bail out gracefully.
+    // See bug 1532712 for details.
+    if (!newRoot.ownerGlobal) {
+      return;
+    }
+
     for (const root of this.roots) {
       if (root === newRoot ||
           root.contains(newRoot) ||
diff --git a/intl/l10n/DocumentL10n.cpp b/intl/l10n/DocumentL10n.cpp
index 7832963bc1b4..bb3d1377f241 100644
--- a/intl/l10n/DocumentL10n.cpp
+++ b/intl/l10n/DocumentL10n.cpp
@@ -351,6 +351,14 @@ already_AddRefed<Promise> DocumentL10n::TranslateElements(
   return MaybeWrapPromise(promise);
 }
 
+void DocumentL10n::PauseObserving(ErrorResult& aRv) {
+  aRv = mDOMLocalization->PauseObserving();
+}
+
+void DocumentL10n::ResumeObserving(ErrorResult& aRv) {
+  aRv = mDOMLocalization->ResumeObserving();
+}
+
 class L10nReadyHandler final : public PromiseNativeHandler {
  public:
   NS_DECL_CYCLE_COLLECTING_ISUPPORTS
diff --git a/intl/l10n/DocumentL10n.h b/intl/l10n/DocumentL10n.h
index a4ae3e9f39e7..85c92d1a23f3 100644
--- a/intl/l10n/DocumentL10n.h
+++ b/intl/l10n/DocumentL10n.h
@@ -125,6 +125,9 @@ class DocumentL10n final : public nsIObserver,
   already_AddRefed<Promise> TranslateElements(
       const Sequence<OwningNonNull<Element>>& aElements, ErrorResult& aRv);
 
+  void PauseObserving(ErrorResult& aRv);
+  void ResumeObserving(ErrorResult& aRv);
+
   Promise* Ready();
 
   void TriggerInitialDocumentTranslation();
diff --git a/intl/l10n/mozIDOMLocalization.idl b/intl/l10n/mozIDOMLocalization.idl
index 536b45835135..d00ead101191 100644
--- a/intl/l10n/mozIDOMLocalization.idl
+++ b/intl/l10n/mozIDOMLocalization.idl
@@ -25,6 +25,10 @@ interface mozIDOMLocalization : nsISupports
 
   void connectRoot(in Element aElement);
   void disconnectRoot(in Element aElement);
+
+  void pauseObserving();
+  void resumeObserving();
+
   Promise translateRoots();
   readonly attribute Promise ready;
 };
diff --git a/js/src/jit/ProcessExecutableMemory.cpp b/js/src/jit/ProcessExecutableMemory.cpp
index da14999dd85e..d395ccf51cab 100644
--- a/js/src/jit/ProcessExecutableMemory.cpp
+++ b/js/src/jit/ProcessExecutableMemory.cpp
@@ -23,6 +23,7 @@
 #ifdef JS_CODEGEN_ARM64
 #  include "jit/arm64/vixl/Cpu-vixl.h"
 #endif
+#include "jit/AtomicOperations.h"
 #include "threading/LockGuard.h"
 #include "threading/Mutex.h"
 #include "util/Windows.h"
@@ -725,6 +726,19 @@ bool js::jit::ReprotectRegion(void* start, size_t size,
 
   execMemory.assertValidAddress(pageStart, size);
 
+  // On weak memory systems, make sure new code is visible on all cores before
+  // addresses of the code are made public.  Now is the latest moment in time
+  // when we can do that, and we're assuming that every other thread that has
+  // written into the memory that is being reprotected here has synchronized
+  // with this thread in such a way that the memory writes have become visible
+  // and we therefore only need to execute the fence once here.  See bug 1529933
+  // for a longer discussion of why this is both necessary and sufficient.
+  //
+  // We use the C++ fence here -- and not AtomicOperations::fenceSeqCst() --
+  // primarily because ReprotectRegion will be called while we construct our own
+  // jitted atomics.  But the C++ fence is sufficient and correct, too.
+  std::atomic_thread_fence(std::memory_order_seq_cst);
+
 #ifdef XP_WIN
   DWORD oldProtect;
   DWORD flags = ProtectionSettingToFlags(protection);