--- a/browser/base/content/browser.css
+++ b/browser/base/content/browser.css
@@ -64,38 +64,16 @@ toolbar[customizable="true"] {
   -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-menubar-stub");
 }
 %endif
 
 #toolbar-menubar[autohide="true"] {
   -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#toolbar-menubar-autohide");
 }
 
-#addon-bar {
-  -moz-binding: url("chrome://browser/content/customizableui/toolbar.xml#addonbar-delegating");
-  visibility: visible;
-  margin: 0;
-  height: 0 !important;
-  overflow: hidden;
-  padding: 0;
-  border: 0 none;
-}
-
-#addonbar-closebutton {
-  visibility: visible;
-  height: 0 !important;
-}
-
-#status-bar {
-  height: 0 !important;
-  -moz-binding: none;
-  padding: 0;
-  margin: 0;
-}
-
 panelmultiview {
   -moz-binding: url("chrome://browser/content/customizableui/panelUI.xml#panelmultiview");
 }
 
 photonpanelmultiview {
   -moz-binding: url("chrome://browser/content/customizableui/panelUI.xml#photonpanelmultiview");
 }
 

--- a/browser/base/content/browser.js
+++ b/browser/base/content/browser.js
@@ -8650,17 +8650,17 @@ var ToolbarIconColor = {
       case "toolbarvisibilitychange":
         // toolbar changes dont require reset of the cached color values
         break;
       case "tabsintitlebar":
         this._windowState.tabsintitlebar = reasonValue;
         break;
     }
 
-    let toolbarSelector = "#navigator-toolbox > toolbar:not([collapsed=true]):not(#addon-bar)";
+    let toolbarSelector = "#navigator-toolbox > toolbar:not([collapsed=true])";
     if (AppConstants.platform == "macosx")
       toolbarSelector += ":not([type=menubar])";
 
     // The getComputedStyle calls and setting the brighttext are separated in
     // two loops to avoid flushing layout and making it dirty repeatedly.
     let cachedLuminances = this._toolbarLuminanceCache;
     let luminances = new Map();
     for (let toolbar of document.querySelectorAll(toolbarSelector)) {

--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -1127,23 +1127,16 @@
                          tooltip="bhTooltip" popupsinherittooltip="true"
                          context="placesContext"/>
             </toolbarbutton>
           </hbox>
         </hbox>
       </toolbaritem>
     </toolbar>
 
-    <!-- This is a shim which will go away ASAP. See bug 749804 for details -->
-    <toolbar id="addon-bar" toolbar-delegate="nav-bar" mode="icons" iconsize="small"
-             customizable="true">
-      <hbox id="addonbar-closebutton"/>
-      <statusbar id="status-bar"/>
-    </toolbar>
-
     <toolbarpalette id="BrowserToolbarPalette">
 
       <toolbarbutton id="print-button" class="toolbarbutton-1 chromeclass-toolbar-additional"
 #ifdef XP_MACOSX
                      command="cmd_print"
                      tooltip="dynamic-shortcut-tooltip"
 #else
                      command="cmd_printPreview"

--- a/browser/components/customizableui/CustomizableUI.jsm
+++ b/browser/components/customizableui/CustomizableUI.jsm
@@ -245,32 +245,24 @@ var CustomizableUIInternal = {
       legacy: true,
       type: CustomizableUI.TYPE_TOOLBAR,
       defaultPlacements: [
         "personal-bookmarks",
       ],
       defaultCollapsed: true,
     }, true);
 
-    this.registerArea(CustomizableUI.AREA_ADDONBAR, {
-      type: CustomizableUI.TYPE_TOOLBAR,
-      legacy: true,
-      defaultPlacements: ["addonbar-closebutton", "status-bar"],
-      defaultCollapsed: false,
-    }, true);
-
     SearchWidgetTracker.init();
   },
 
   get _builtinToolbars() {
     let toolbars = new Set([
       CustomizableUI.AREA_NAVBAR,
       CustomizableUI.AREA_BOOKMARKS,
       CustomizableUI.AREA_TABSTRIP,
-      CustomizableUI.AREA_ADDONBAR,
     ]);
     if (AppConstants.platform != "macosx") {
       toolbars.add(CustomizableUI.AREA_MENUBAR);
     }
     return toolbars;
   },
 
   _defineBuiltInWidgets() {
@@ -2871,22 +2863,16 @@ this.CustomizableUI = {
    * Constant reference to the ID of the tabstrip toolbar.
    */
   AREA_TABSTRIP: "TabsToolbar",
   /**
    * Constant reference to the ID of the bookmarks toolbar.
    */
   AREA_BOOKMARKS: "PersonalToolbar",
   /**
-   * Constant reference to the ID of the addon-bar toolbar shim.
-   * Do not use, this will be removed as soon as reasonably possible.
-   * @deprecated
-   */
-  AREA_ADDONBAR: "addon-bar",
-  /**
    * Constant reference to the ID of the non-dymanic (fixed) list in the overflow panel.
    */
   AREA_FIXED_OVERFLOW_PANEL: "widget-overflow-fixed-list",
 
   /**
    * Constant indicating the area is a menu panel.
    */
   TYPE_MENU_PANEL: "menu-panel",

--- a/browser/components/customizableui/content/toolbar.xml
+++ b/browser/components/customizableui/content/toolbar.xml
@@ -383,236 +383,9 @@
             draggableThis.mouseDownCheck = function(e) {
               return this._dragBindingAlive;
             };
           } catch (e) {}
         }
       ]]></constructor>
     </implementation>
   </binding>
-
-
-<!-- This is a peculiar binding. It is here to deal with overlayed/inserted add-on content,
-      and immediately direct such content elsewhere. -->
-  <binding id="addonbar-delegating">
-    <implementation>
-      <constructor><![CDATA[
-          // Reading these immediately so nobody messes with them anymore:
-          this._delegatingToolbar = this.getAttribute("toolbar-delegate");
-          this._wasCollapsed = this.getAttribute("collapsed") == "true";
-          // Leaving those in here to unbreak some code:
-          if (document.readyState == "complete") {
-            this._init();
-          } else {
-            // Need to wait until XUL overlays are loaded. See bug 554279.
-            let self = this;
-            document.addEventListener("readystatechange", function onReadyStateChange() {
-              if (document.readyState != "complete")
-                return;
-              document.removeEventListener("readystatechange", onReadyStateChange);
-              self._init();
-            });
-          }
-      ]]></constructor>
-
-      <method name="_init">
-        <body><![CDATA[
-          // Searching for the toolbox palette in the toolbar binding because
-          // toolbars are constructed first.
-          let toolbox = this.toolbox;
-          if (toolbox && !toolbox.palette) {
-            for (let node of toolbox.children) {
-              if (node.localName == "toolbarpalette") {
-                // Hold on to the palette but remove it from the document.
-                toolbox.palette = node;
-                toolbox.removeChild(node);
-              }
-            }
-          }
-
-          // pass the current set of children for comparison with placements:
-          let children = [];
-          for (let node of this.childNodes) {
-            if (node.getAttribute("skipintoolbarset") != "true" && node.id) {
-              // Force everything to be removable so that buildArea can chuck stuff
-              // out if the user has customized things / we've been here before:
-              if (!this._whiteListed.has(node.id)) {
-                node.setAttribute("removable", "true");
-              }
-              children.push(node);
-            }
-          }
-          CustomizableUI.registerToolbarNode(this, children);
-          let existingMigratedItems = (this.getAttribute("migratedset") || "").split(",");
-          for (let migratedItem of existingMigratedItems.filter((x) => !!x)) {
-            this._currentSetMigrated.add(migratedItem);
-          }
-          this.evictNodes();
-          // We can't easily use |this| or strong bindings for the observer fn here
-          // because that creates leaky circular references when the node goes away,
-          // and XBL destructors are unreliable.
-          let mutationObserver = new MutationObserver(function(mutations) {
-            if (!mutations.length) {
-              return;
-            }
-            let toolbar = mutations[0].target;
-            // Can't use our own attribute because we might not have one if we're set to
-            // collapsed
-            let areCustomizing = toolbar.ownerDocument.documentElement.getAttribute("customizing");
-            if (!toolbar._isModifying && !areCustomizing) {
-              toolbar.evictNodes();
-            }
-          });
-          mutationObserver.observe(this, {childList: true});
-        ]]></body>
-      </method>
-      <method name="evictNodes">
-        <body><![CDATA[
-          this._isModifying = true;
-          let i = this.childNodes.length;
-          while (i--) {
-            let node = this.childNodes[i];
-            if (this.childNodes[i].id) {
-              this.evictNode(this.childNodes[i]);
-            } else {
-              node.remove();
-            }
-          }
-          this._isModifying = false;
-          this._updateMigratedSet();
-        ]]></body>
-      </method>
-      <method name="evictNode">
-        <parameter name="aNode"/>
-        <body>
-        <![CDATA[
-          if (this._whiteListed.has(aNode.id) || CustomizableUI.isSpecialWidget(aNode.id)) {
-            return;
-          }
-          const kItemMaxWidth = 100;
-          let oldParent = aNode.parentNode;
-          aNode.setAttribute("removable", "true");
-          this._currentSetMigrated.add(aNode.id);
-
-          let movedOut = false;
-          if (!this._wasCollapsed) {
-            try {
-              let nodeWidth = aNode.getBoundingClientRect().width;
-              if (nodeWidth == 0 || nodeWidth > kItemMaxWidth) {
-                throw new Error(aNode.id + " is too big (" + nodeWidth +
-                                "px wide), moving to the palette");
-              }
-              CustomizableUI.addWidgetToArea(aNode.id, this._delegatingToolbar);
-              movedOut = true;
-            } catch (ex) {
-              // This will throw if the node is too big, or can't be moved there for
-              // some reason. Report this:
-              Cu.reportError(ex);
-            }
-          }
-
-          /* We won't have moved the widget if either the add-on bar was collapsed,
-           * or if it was too wide to be inserted into the navbar. */
-          if (!movedOut) {
-            try {
-              CustomizableUI.removeWidgetFromArea(aNode.id);
-            } catch (ex) {
-              Cu.reportError(ex);
-              aNode.remove();
-            }
-          }
-
-          // Surprise: addWidgetToArea(palette) will get you nothing if the palette
-          // is not constructed yet. Fix:
-          if (aNode.parentNode == oldParent) {
-            let palette = this.toolbox.palette;
-            if (palette && oldParent != palette) {
-              palette.appendChild(aNode);
-            }
-          }
-        ]]></body>
-      </method>
-      <method name="insertItem">
-        <parameter name="aId"/>
-        <parameter name="aBeforeElt"/>
-        <parameter name="aWrapper"/>
-        <body><![CDATA[
-          if (aWrapper) {
-            Cu.reportError("Can't insert " + aId + ": using insertItem " +
-                           "no longer supports wrapper elements.");
-            return null;
-          }
-
-          let widget = CustomizableUI.getWidget(aId);
-          widget = widget && widget.forWindow(window);
-          let node = widget && widget.node;
-          if (!node) {
-            return null;
-          }
-
-          this._isModifying = true;
-          // Temporarily add it here so it can have a width, then ditch it:
-          this.appendChild(node);
-          this.evictNode(node);
-          this._isModifying = false;
-          this._updateMigratedSet();
-          // We will now have moved stuff around; kick off some events
-          // so add-ons know we've just moved their stuff:
-          // XXXgijs: only in this window. It's hard to know for sure what's the right
-          // thing to do here - typically insertItem is used on each window, so
-          // this seems to make the most sense, even if some of the effects of
-          // evictNode might affect multiple windows.
-          CustomizableUI.dispatchToolboxEvent("customizationchange", {}, window);
-          CustomizableUI.dispatchToolboxEvent("aftercustomization", {}, window);
-          return node;
-        ]]></body>
-      </method>
-      <method name="getMigratedItems">
-        <body><![CDATA[
-          return [...this._currentSetMigrated];
-        ]]></body>
-      </method>
-      <method name="_updateMigratedSet">
-        <body><![CDATA[
-          let newMigratedItems = this.getMigratedItems().join(",");
-          if (this.getAttribute("migratedset") != newMigratedItems) {
-            this.setAttribute("migratedset", newMigratedItems);
-            this.ownerDocument.persist(this.id, "migratedset");
-          }
-        ]]></body>
-      </method>
-      <property name="customizationTarget" readonly="true">
-        <getter><![CDATA[
-          return this;
-        ]]></getter>
-      </property>
-      <property name="currentSet">
-        <getter><![CDATA[
-          return Array.from(this.children, node => node.id).join(",");
-        ]]></getter>
-        <setter><![CDATA[
-          let v = val.split(",");
-          let newButtons = v.filter(x => x && (!this._whiteListed.has(x) &&
-                                               !CustomizableUI.isSpecialWidget(x) &&
-                                               !this._currentSetMigrated.has(x)));
-          for (let newButton of newButtons) {
-            this._currentSetMigrated.add(newButton);
-            this.insertItem(newButton);
-          }
-          this._updateMigratedSet();
-        ]]></setter>
-      </property>
-      <property name="toolbox" readonly="true">
-        <getter><![CDATA[
-          if (!this._toolbox && this.parentNode &&
-              this.parentNode.localName == "toolbox") {
-            this._toolbox = this.parentNode;
-          }
-
-          return this._toolbox;
-        ]]></getter>
-      </property>
-      <field name="_whiteListed" readonly="true">new Set(["addonbar-closebutton", "status-bar"])</field>
-      <field name="_isModifying">false</field>
-      <field name="_currentSetMigrated">new Set()</field>
-    </implementation>
-  </binding>
 </bindings>

--- a/browser/components/customizableui/test/browser.ini
+++ b/browser/components/customizableui/test/browser.ini
@@ -51,17 +51,16 @@ skip-if = os == "mac"
 [browser_934951_zoom_in_toolbar.js]
 [browser_938980_navbar_collapsed.js]
 [browser_938995_indefaultstate_nonremovable.js]
 [browser_940013_registerToolbarNode_calls_registerArea.js]
 [browser_940307_panel_click_closure_handling.js]
 [browser_940946_removable_from_navbar_customizemode.js]
 [browser_941083_invalidate_wrapper_cache_createWidget.js]
 [browser_942581_unregisterArea_keeps_placements.js]
-[browser_943683_migration_test.js]
 [browser_944887_destroyWidget_should_destroy_in_palette.js]
 [browser_945739_showInPrivateBrowsing_customize_mode.js]
 [browser_947914_button_addons.js]
 skip-if = os == "linux" # Intermittent failures
 [browser_947914_button_copy.js]
 subsuite = clipboard
 skip-if = os == "linux" # Intermittent failures on Linux
 [browser_947914_button_cut.js]
@@ -96,17 +95,16 @@ skip-if = os == "linux" # Intermittent f
 [browser_967000_button_charEncoding.js]
 [browser_967000_button_feeds.js]
 [browser_968565_insert_before_hidden_items.js]
 [browser_969427_recreate_destroyed_widget_after_reset.js]
 [browser_969661_character_encoding_navbar_disabled.js]
 [browser_970511_undo_restore_default.js]
 [browser_972267_customizationchange_events.js]
 [browser_973641_button_addon.js]
-[browser_973932_addonbar_currentset.js]
 [browser_975719_customtoolbars_behaviour.js]
 [browser_976792_insertNodeInWindow.js]
 skip-if = os == "linux"
 [browser_978084_dragEnd_after_move.js]
 [browser_980155_add_overflow_toolbar.js]
 [browser_981305_separator_insertion.js]
 [browser_981418-widget-onbeforecreated-handler.js]
 [browser_982656_restore_defaults_builtin_widgets.js]

deleted file mode 100644
--- a/browser/components/customizableui/test/browser_943683_migration_test.js
+++ /dev/null
@@ -1,50 +0,0 @@
-/* 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/. */
-
-"use strict";
-
-const kWidgetId = "test-addonbar-migration";
-const kWidgetId2 = "test-addonbar-migration2";
-
-var addonbar = document.getElementById(CustomizableUI.AREA_ADDONBAR);
-var navbar = document.getElementById(CustomizableUI.AREA_NAVBAR);
-
-var btn;
-var btn2;
-
-// Check we migrate normal stuff to the navbar
-add_task(async function() {
-  btn = createDummyXULButton(kWidgetId, "Test");
-  btn2 = createDummyXULButton(kWidgetId2, "Test2");
-  addonbar.insertItem(btn.id);
-  ok(btn.parentNode == navbar.customizationTarget, "Button should end up in navbar");
-  let migrationArray = addonbar.getMigratedItems();
-  is(migrationArray.length, 1, "Should have migrated 1 item");
-  is(migrationArray[0], kWidgetId, "Should have migrated our 1 item");
-
-  addonbar.currentSet = addonbar.currentSet + "," + kWidgetId2;
-  ok(btn2.parentNode == navbar.customizationTarget, "Second button should end up in the navbar");
-  migrationArray = addonbar.getMigratedItems();
-  is(migrationArray.length, 2, "Should have migrated 2 items");
-  isnot(migrationArray.indexOf(kWidgetId2), -1, "Should have migrated our second item");
-
-  let otherWindow = await openAndLoadWindow(undefined, true);
-  try {
-    let addonBar = otherWindow.document.getElementById("addon-bar");
-    let otherMigrationArray = addonBar.getMigratedItems();
-    is(migrationArray.length, otherMigrationArray.length,
-       "Other window should have the same number of migrated items.");
-    if (migrationArray.length == otherMigrationArray.length) {
-      for (let widget of migrationArray) {
-        isnot(otherMigrationArray.indexOf(widget), -1,
-              "Migrated widget " + widget + " should also be listed as migrated in the other window.");
-      }
-    }
-  } finally {
-    await promiseWindowClosed(otherWindow);
-  }
-  btn.remove();
-  btn2.remove();
-  CustomizableUI.reset();
-});

deleted file mode 100644
--- a/browser/components/customizableui/test/browser_973932_addonbar_currentset.js
+++ /dev/null
@@ -1,30 +0,0 @@
-/* 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/. */
-
-"use strict";
-
-var addonbarID = CustomizableUI.AREA_ADDONBAR;
-var addonbar = document.getElementById(addonbarID);
-
-// Check that currentset is correctly updated after a reset:
-add_task(async function() {
-  let placements = CustomizableUI.getWidgetIdsInArea(addonbarID);
-  is(placements.join(","), addonbar.getAttribute("currentset"), "Addon-bar currentset should match default placements");
-  ok(CustomizableUI.inDefaultState, "Should be in default state");
-  info("Adding a spring to add-on bar shim");
-  CustomizableUI.addWidgetToArea("spring", addonbarID, 1);
-  ok(addonbar.getElementsByTagName("toolbarspring").length, "There should be a spring in the toolbar");
-  ok(!CustomizableUI.inDefaultState, "Should no longer be in default state");
-  placements = CustomizableUI.getWidgetIdsInArea(addonbarID);
-  is(placements.join(","), addonbar.getAttribute("currentset"), "Addon-bar currentset should match placements after spring addition");
-
-  await startCustomizing();
-  await gCustomizeMode.reset();
-  ok(CustomizableUI.inDefaultState, "Should be in default state after reset");
-  placements = CustomizableUI.getWidgetIdsInArea(addonbarID);
-  is(placements.join(","), addonbar.getAttribute("currentset"), "Addon-bar currentset should match default placements after reset");
-  ok(!addonbar.getElementsByTagName("toolbarspring").length, "There should be no spring in the toolbar");
-  await endCustomizing();
-});
-

--- a/browser/components/nsBrowserGlue.js
+++ b/browser/components/nsBrowserGlue.js
@@ -1786,17 +1786,17 @@ BrowserGlue.prototype = {
           xulStore.setValue(BROWSER_DOCURL, "nav-bar", "currentset", currentset);
         }
       }
     }
 
     if (currentUIVersion < 18) {
       // Remove iconsize and mode from all the toolbars
       let toolbars = ["navigator-toolbox", "nav-bar", "PersonalToolbar",
-                      "addon-bar", "TabsToolbar", "toolbar-menubar"];
+                      "TabsToolbar", "toolbar-menubar"];
       for (let resourceName of ["mode", "iconsize"]) {
         for (let toolbarId of toolbars) {
           xulStore.removeValue(BROWSER_DOCURL, toolbarId, resourceName);
         }
       }
     }
 
     if (currentUIVersion < 19) {
@@ -1967,17 +1967,17 @@ BrowserGlue.prototype = {
 
     if (currentUIVersion < 38) {
       LoginHelper.removeLegacySignonFiles();
     }
 
     if (currentUIVersion < 39) {
       // Remove the 'defaultset' value for all the toolbars
       let toolbars = ["nav-bar", "PersonalToolbar",
-                      "addon-bar", "TabsToolbar", "toolbar-menubar"];
+                      "TabsToolbar", "toolbar-menubar"];
       for (let toolbarId of toolbars) {
         xulStore.removeValue(BROWSER_DOCURL, toolbarId, "defaultset");
       }
     }
 
     if (currentUIVersion < 40) {
       const kOldSafeBrowsingPref = "browser.safebrowsing.enabled";
       // Default value is set to true, a user pref means that the pref was

--- a/browser/themes/osx/browser.css
+++ b/browser/themes/osx/browser.css
@@ -136,17 +136,17 @@
   border-top: 1px solid rgba(0,0,0,0.65);
 }
 
 #navigator-toolbox > toolbar:not(#TabsToolbar) {
   -moz-appearance: none;
   background: var(--toolbar-bgcolor);
 }
 
-#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar):not(#addon-bar) {
+#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar) {
   /* add extra padding to compensate the bottom border */
   padding-bottom: 2px;
 }
 
 /* Draw the bottom border of the tabs toolbar when it's not using
    -moz-appearance: toolbar. */
 #main-window:-moz-any([sizemode="fullscreen"],[customize-entered]) #TabsToolbar:not([collapsed="true"]) + #nav-bar,
 #main-window:not([tabsintitlebar]) #TabsToolbar:not([collapsed="true"]) + #nav-bar,

--- a/browser/themes/shared/browser.inc.css
+++ b/browser/themes/shared/browser.inc.css
@@ -13,24 +13,24 @@
 %endif
 {
   padding-inline-start: 40px;
 }
 %endif
 
 /* Bookmark toolbar */
 
-#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar):not(#addon-bar) {
+#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar) {
   overflow: -moz-hidden-unscrollable;
   max-height: 4em;
   transition: min-height 170ms ease-out, max-height 170ms ease-out;
   padding: 0 4px 1px;
 }
 
-#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar):not(#addon-bar)[collapsed=true] {
+#navigator-toolbox > toolbar:not(#toolbar-menubar):not(#TabsToolbar):not(#nav-bar)[collapsed=true] {
   min-height: 0.1px;
   max-height: 0;
   transition: min-height 170ms ease-out, max-height 170ms ease-out, visibility 170ms linear;
 }
 
 /* Go button */
 .urlbar-go-button {
   padding: 0 3px;