--- a/browser/components/customizableui/test/browser_884402_customize_from_overflow.js
+++ b/browser/components/customizableui/test/browser_884402_customize_from_overflow.js
@@ -27,20 +27,20 @@ add_task(async function() {
 
   let chevron = document.getElementById("nav-bar-overflow-button");
   let shownPanelPromise = promisePanelElementShown(window, overflowPanel);
   chevron.click();
   await shownPanelPromise;
 
   let contextMenu = document.getElementById("toolbar-context-menu");
   let shownContextPromise = popupShown(contextMenu);
-  let homeButton = document.getElementById("home-button");
-  ok(homeButton, "home-button was found");
-  is(homeButton.getAttribute("overflowedItem"), "true", "Home button is overflowing");
-  EventUtils.synthesizeMouse(homeButton, 2, 2, {type: "contextmenu", button: 2});
+  let sidebarButton = document.getElementById("sidebar-button");
+  ok(sidebarButton, "sidebar-button was found");
+  is(sidebarButton.getAttribute("overflowedItem"), "true", "Sidebar button is overflowing");
+  EventUtils.synthesizeMouse(sidebarButton, 2, 2, {type: "contextmenu", button: 2});
   await shownContextPromise;
 
   is(overflowPanel.state, "open", "The widget overflow panel should still be open.");
 
   let expectedEntries = [
     [".customize-context-moveToPanel", true],
     [".customize-context-removeFromToolbar", true],
     ["---"]
@@ -60,23 +60,23 @@ add_task(async function() {
   let moveToPanel = contextMenu.querySelector(".customize-context-moveToPanel");
   if (moveToPanel) {
     moveToPanel.click();
   }
   contextMenu.hidePopup();
   await hiddenContextPromise;
   await hiddenPromise;
 
-  let homeButtonPlacement = CustomizableUI.getPlacementOfWidget("home-button");
-  ok(homeButtonPlacement, "Home button should still have a placement");
-  is(homeButtonPlacement && homeButtonPlacement.area, "PanelUI-contents", "Home button should be in the panel now");
+  let sidebarButtonPlacement = CustomizableUI.getPlacementOfWidget("sidebar-button");
+  ok(sidebarButtonPlacement, "Sidebar button should still have a placement");
+  is(sidebarButtonPlacement && sidebarButtonPlacement.area, "PanelUI-contents", "Sidebar button should be in the panel now");
   CustomizableUI.reset();
 
   // In some cases, it can take a tick for the navbar to overflow again. Wait for it:
   await waitForCondition(() => navbar.hasAttribute("overflowing"));
   ok(navbar.hasAttribute("overflowing"), "Should have an overflowing toolbar.");
 
-  homeButtonPlacement = CustomizableUI.getPlacementOfWidget("home-button");
-  ok(homeButtonPlacement, "Home button should still have a placement");
-  is(homeButtonPlacement && homeButtonPlacement.area, "nav-bar", "Home button should be back in the navbar now");
+  sidebarButtonPlacement = CustomizableUI.getPlacementOfWidget("sidebar-button");
+  ok(sidebarButtonPlacement, "Sidebar button should still have a placement");
+  is(sidebarButtonPlacement && sidebarButtonPlacement.area, "nav-bar", "Sidebar button should be back in the navbar now");
 
-  is(homeButton.getAttribute("overflowedItem"), "true", "Home button should still be overflowed");
+  is(sidebarButton.getAttribute("overflowedItem"), "true", "Sidebar button should still be overflowed");
 });

--- a/browser/components/customizableui/test/browser_914138_widget_API_overflowable_toolbar.js
+++ b/browser/components/customizableui/test/browser_914138_widget_API_overflowable_toolbar.js
@@ -5,52 +5,52 @@
 "use strict";
 
 var navbar = document.getElementById(CustomizableUI.AREA_NAVBAR);
 var overflowList = document.getElementById(navbar.getAttribute("overflowtarget"));
 
 const kTestBtn1 = "test-addWidgetToArea-overflow";
 const kTestBtn2 = "test-removeWidgetFromArea-overflow";
 const kTestBtn3 = "test-createWidget-overflow";
-const kHomeBtn = "home-button";
+const kSidebarBtn = "sidebar-button";
 const kDownloadsBtn = "downloads-button";
 const kSearchBox = "search-container";
 
 var originalWindowWidth;
 
 // Adding a widget should add it next to the widget it's being inserted next to.
 add_task(async function() {
   originalWindowWidth = window.outerWidth;
   createDummyXULButton(kTestBtn1, "Test");
   ok(!navbar.hasAttribute("overflowing"), "Should start with a non-overflowing toolbar.");
   ok(CustomizableUI.inDefaultState, "Should start in default state.");
 
   window.resizeTo(400, window.outerHeight);
   await waitForCondition(() => navbar.hasAttribute("overflowing"));
   ok(navbar.hasAttribute("overflowing"), "Should have an overflowing toolbar.");
-  ok(!navbar.querySelector("#" + kHomeBtn), "Home button should no longer be in the navbar");
-  let homeBtnNode = overflowList.querySelector("#" + kHomeBtn);
-  ok(homeBtnNode, "Home button should be overflowing");
-  ok(homeBtnNode && homeBtnNode.getAttribute("overflowedItem") == "true", "Home button should have overflowedItem attribute");
+  ok(!navbar.querySelector("#" + kSidebarBtn), "Sidebar button should no longer be in the navbar");
+  let sidebarBtnNode = overflowList.querySelector("#" + kSidebarBtn);
+  ok(sidebarBtnNode, "Sidebar button should be overflowing");
+  ok(sidebarBtnNode && sidebarBtnNode.getAttribute("overflowedItem") == "true", "Sidebar button should have overflowedItem attribute");
 
-  let placementOfHomeButton = CustomizableUI.getWidgetIdsInArea(navbar.id).indexOf(kHomeBtn);
-  CustomizableUI.addWidgetToArea(kTestBtn1, navbar.id, placementOfHomeButton);
+  let placementOfSidebarButton = CustomizableUI.getWidgetIdsInArea(navbar.id).indexOf(kSidebarBtn);
+  CustomizableUI.addWidgetToArea(kTestBtn1, navbar.id, placementOfSidebarButton);
   ok(!navbar.querySelector("#" + kTestBtn1), "New button should not be in the navbar");
   let newButtonNode = overflowList.querySelector("#" + kTestBtn1);
   ok(newButtonNode, "New button should be overflowing");
   ok(newButtonNode && newButtonNode.getAttribute("overflowedItem") == "true", "New button should have overflowedItem attribute");
   let nextEl = newButtonNode && newButtonNode.nextSibling;
-  is(nextEl && nextEl.id, kHomeBtn, "Test button should be next to home button.");
+  is(nextEl && nextEl.id, kSidebarBtn, "Test button should be next to sidebar button.");
 
   window.resizeTo(originalWindowWidth, window.outerHeight);
   await waitForCondition(() => !navbar.hasAttribute("overflowing"));
   ok(!navbar.hasAttribute("overflowing"), "Should not have an overflowing toolbar.");
-  ok(navbar.querySelector("#" + kHomeBtn), "Home button should be in the navbar");
-  ok(homeBtnNode && (homeBtnNode.getAttribute("overflowedItem") != "true"), "Home button should no longer have overflowedItem attribute");
-  ok(!overflowList.querySelector("#" + kHomeBtn), "Home button should no longer be overflowing");
+  ok(navbar.querySelector("#" + kSidebarBtn), "Sidebar button should be in the navbar");
+  ok(sidebarBtnNode && (sidebarBtnNode.getAttribute("overflowedItem") != "true"), "Sidebar button should no longer have overflowedItem attribute");
+  ok(!overflowList.querySelector("#" + kSidebarBtn), "Sidebar button should no longer be overflowing");
   ok(navbar.querySelector("#" + kTestBtn1), "Test button should be in the navbar");
   ok(!overflowList.querySelector("#" + kTestBtn1), "Test button should no longer be overflowing");
   ok(newButtonNode && (newButtonNode.getAttribute("overflowedItem") != "true"), "New button should no longer have overflowedItem attribute");
   let el = document.getElementById(kTestBtn1);
   if (el) {
     CustomizableUI.removeWidgetFromArea(kTestBtn1);
     el.remove();
   }
@@ -92,20 +92,20 @@ add_task(async function() {
 add_task(async function() {
   originalWindowWidth = window.outerWidth;
   ok(!navbar.hasAttribute("overflowing"), "Should start with a non-overflowing toolbar.");
   ok(CustomizableUI.inDefaultState, "Should start in default state.");
 
   window.resizeTo(400, window.outerHeight);
   await waitForCondition(() => navbar.hasAttribute("overflowing"));
   ok(navbar.hasAttribute("overflowing"), "Should have an overflowing toolbar.");
-  ok(!navbar.querySelector("#" + kHomeBtn), "Home button should no longer be in the navbar");
-  let homeBtnNode = overflowList.querySelector("#" + kHomeBtn);
-  ok(homeBtnNode, "Home button should be overflowing");
-  ok(homeBtnNode && homeBtnNode.getAttribute("overflowedItem") == "true", "Home button should have overflowedItem class");
+  ok(!navbar.querySelector("#" + kSidebarBtn), "Sidebar button should no longer be in the navbar");
+  let sidebarBtnNode = overflowList.querySelector("#" + kSidebarBtn);
+  ok(sidebarBtnNode, "Sidebar button should be overflowing");
+  ok(sidebarBtnNode && sidebarBtnNode.getAttribute("overflowedItem") == "true", "Sidebar button should have overflowedItem class");
 
   let testBtnSpec = {id: kTestBtn3, label: "Overflowable widget test", defaultArea: "nav-bar"};
   CustomizableUI.createWidget(testBtnSpec);
   let testNode = overflowList.querySelector("#" + kTestBtn3);
   ok(testNode, "Test button should be overflowing");
   ok(testNode && testNode.getAttribute("overflowedItem") == "true", "Test button should have overflowedItem class");
 
   CustomizableUI.destroyWidget(kTestBtn3);

--- a/browser/components/extensions/test/browser/browser_ext_user_events.js
+++ b/browser/components/extensions/test/browser/browser_ext_user_events.js
@@ -40,16 +40,19 @@ add_task(async function testSources() {
   });
 
   async function check(what) {
     let result = await extension.awaitMessage("request");
     ok(result.success, `request() did not throw when called from ${what}`);
     is(result.result, true, `request() succeeded when called from ${what}`);
   }
 
+  // Remove Sidebar button to prevent pushing extension button to overflow menu
+  CustomizableUI.removeWidgetFromArea("sidebar-button");
+
   await extension.startup();
 
   await extension.awaitMessage("page-action-shown");
   clickPageAction(extension);
   await check("page action click");
 
   clickBrowserAction(extension);
   await check("browser action click");
@@ -61,10 +64,12 @@ add_task(async function testSources() {
   let items = menu.getElementsByAttribute("label", "test user events");
   is(items.length, 1, "Found context menu item");
   EventUtils.synthesizeMouseAtCenter(items[0], {});
   await check("context menu click");
 
   await BrowserTestUtils.removeTab(tab);
 
   await extension.unload();
+
+  registerCleanupFunction(() => CustomizableUI.reset());
 });
 

--- a/browser/modules/test/browser/browser_BrowserUITelemetry_defaults.js
+++ b/browser/modules/test/browser/browser_BrowserUITelemetry_defaults.js
@@ -18,20 +18,15 @@ function test() {
 
   let result = BrowserUITelemetry._getWindowMeasurements(window, 0);
 
   // Bug 1278176 - DevEdition always reports the developer-button is moved.
   if (!AppConstants.MOZ_DEV_EDITION) {
     Assert.deepEqual(result.defaultMoved, []);
   }
   Assert.deepEqual(result.nondefaultAdded, []);
-  // This one is a bit weird - the "social-share-button" is dynamically added
-  // to the toolbar as the feature is first used - but it's listed as being in
-  // the toolbar by default so it doesn't end up in nondefaultAdded once it
-  // is created. The end result is that it ends up in defaultRemoved before
-  // the feature has been activated.
-  // Bug 1273358 exists to fix this.
-  Assert.deepEqual(result.defaultRemoved, ["social-share-button"]);
+
+  Assert.deepEqual(result.defaultRemoved, []);
 
   // And mochi insists there's only a single window with a single tab when
   // starting a test, so check that for good measure.
   Assert.deepEqual(result.visibleTabs, [1]);
 }