--- a/browser/components/customizableui/test/browser_1003588_no_specials_in_panel.js
+++ b/browser/components/customizableui/test/browser_1003588_no_specials_in_panel.js
@@ -15,17 +15,17 @@ function simulateItemDragAndEnd(aToDrag,
     EventUtils.sendDragEvent({ type: "dragend", dataTransfer },
                              aToDrag.parentNode);
   } finally {
     ds.endDragSession(true);
   }
 }
 
 add_task(function* checkNoAddingToPanel() {
-  let area = CustomizableUI.AREA_PANEL;
+  let area = gPhotonStructure ? CustomizableUI.AREA_FIXED_OVERFLOW_PANEL : CustomizableUI.AREA_PANEL;
   let previousPlacements = getAreaWidgetIds(area);
   CustomizableUI.addWidgetToArea("separator", area);
   CustomizableUI.addWidgetToArea("spring", area);
   CustomizableUI.addWidgetToArea("spacer", area);
   assertAreaPlacements(area, previousPlacements);
 
   let oldNumberOfItems = previousPlacements.length;
   if (getAreaWidgetIds(area).length != oldNumberOfItems) {
@@ -56,16 +56,17 @@ add_task(function* checkAddingToToolbar(
   let oldNumberOfItems = previousPlacements.length;
   if (getAreaWidgetIds(area).length != oldNumberOfItems) {
     CustomizableUI.reset();
   }
 });
 
 
 add_task(function* checkDragging() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let startArea = CustomizableUI.AREA_NAVBAR;
   let targetArea = CustomizableUI.AREA_PANEL;
   let startingToolbarPlacements = getAreaWidgetIds(startArea);
   let startingTargetPlacements = getAreaWidgetIds(targetArea);
 
   CustomizableUI.addWidgetToArea("separator", startArea);
   CustomizableUI.addWidgetToArea("spring", startArea);
   CustomizableUI.addWidgetToArea("spacer", startArea);

--- a/browser/components/customizableui/test/browser_1008559_anchor_undo_restore.js
+++ b/browser/components/customizableui/test/browser_1008559_anchor_undo_restore.js
@@ -5,16 +5,17 @@
 
 const kAnchorAttribute = "cui-anchorid";
 
 /**
  * Check that anchor gets set correctly when moving an item from the panel to the toolbar
  * using 'undo'
  */
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   let button = document.getElementById("history-panelmenu");
   is(button.getAttribute(kAnchorAttribute), "PanelUI-menu-button",
      "Button (" + button.id + ") starts out with correct anchor");
 
   let navbar = document.getElementById("nav-bar").customizationTarget;
   simulateItemDrag(button, navbar);
   is(CustomizableUI.getPlacementOfWidget(button.id).area, "nav-bar",

--- a/browser/components/customizableui/test/browser_1087303_button_fullscreen.js
+++ b/browser/components/customizableui/test/browser_1087303_button_fullscreen.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check fullscreen button existence and functionality");
 
   yield PanelUI.show();
 
   let fullscreenButton = document.getElementById("fullscreen-button");
   ok(fullscreenButton, "Fullscreen button appears in Panel Menu");
 
   let fullscreenPromise = promiseFullscreenChange();

--- a/browser/components/customizableui/test/browser_1087303_button_preferences.js
+++ b/browser/components/customizableui/test/browser_1087303_button_preferences.js
@@ -2,16 +2,17 @@
   * 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 newTab = null;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check preferences button existence and functionality");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let preferencesButton = document.getElementById("preferences-button");
   ok(preferencesButton, "Preferences button exists in Panel Menu");
   preferencesButton.click();

--- a/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js
+++ b/browser/components/customizableui/test/browser_876926_customize_mode_wrapping.js
@@ -150,16 +150,17 @@ function createXULButtonForWindow(win) {
 function removeXULButtonForWindow(win) {
   win.gNavToolbox.palette.querySelector(`#${kXULWidgetId}`).remove();
 }
 
 var otherWin;
 
 // Moving widgets in two windows, one with customize mode and one without, should work.
 add_task(function* MoveWidgetsInTwoWindows() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   otherWin = yield openAndLoadWindow(null, true);
   yield otherWin.PanelUI.ensureReady();
   // Create the XUL button to use in the test in both windows.
   createXULButtonForWindow(window);
   createXULButtonForWindow(otherWin);
   ok(CustomizableUI.inDefaultState, "Should start in default state");
 

--- a/browser/components/customizableui/test/browser_876944_customize_mode_create_destroy.js
+++ b/browser/components/customizableui/test/browser_876944_customize_mode_create_destroy.js
@@ -4,16 +4,17 @@
 
 "use strict";
 
 const kTestWidget1 = "test-customize-mode-create-destroy1";
 const kTestWidget2 = "test-customize-mode-create-destroy2";
 
 // Creating and destroying a widget should correctly wrap/unwrap stuff
 add_task(function* testWrapUnwrap() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   CustomizableUI.createWidget({id: kTestWidget1, label: "Pretty label", tooltiptext: "Pretty tooltip"});
   let elem = document.getElementById(kTestWidget1);
   let wrapper = document.getElementById("wrapper-" + kTestWidget1);
   ok(elem, "There should be an item");
   ok(wrapper, "There should be a wrapper");
   is(wrapper.firstChild.id, kTestWidget1, "Wrapper should have test widget");
   is(wrapper.parentNode.id, "customization-palette", "Wrapper should be in palette");

--- a/browser/components/customizableui/test/browser_878452_drag_to_panel.js
+++ b/browser/components/customizableui/test/browser_878452_drag_to_panel.js
@@ -1,16 +1,17 @@
 /* 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";
 
 // Dragging an item from the palette to another button in the panel should work.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   let btn = document.getElementById("feed-button");
   let placements = getAreaWidgetIds(CustomizableUI.AREA_PANEL);
 
   let lastButtonIndex = placements.length - 1;
   let lastButton = placements[lastButtonIndex];
   let placementsAfterInsert = placements.slice(0, lastButtonIndex).concat(["feed-button", lastButton]);
   let lastButtonNode = document.getElementById(lastButton);

--- a/browser/components/customizableui/test/browser_880164_customization_context_menus.js
+++ b/browser/components/customizableui/test/browser_880164_customization_context_menus.js
@@ -6,16 +6,17 @@
 
 requestLongerTimeout(2);
 
 const isOSX = (Services.appinfo.OS === "Darwin");
 
 // Right-click on the home button should
 // show a context menu with options to move it.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let contextMenu = document.getElementById("toolbar-context-menu");
   let shownPromise = popupShown(contextMenu);
   let homeButton = document.getElementById("home-button");
   EventUtils.synthesizeMouse(homeButton, 2, 2, {type: "contextmenu", button: 2 });
   yield shownPromise;
 
   let expectedEntries = [
     [".customize-context-moveToPanel", true],

--- a/browser/components/customizableui/test/browser_880382_drag_wide_widgets_in_panel.js
+++ b/browser/components/customizableui/test/browser_880382_drag_wide_widgets_in_panel.js
@@ -3,16 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 requestLongerTimeout(5);
 
 // Dragging the zoom controls to be before the print button should not move any controls.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   let zoomControls = document.getElementById("zoom-controls");
   let printButton = document.getElementById("print-button");
   let placementsAfterMove = ["edit-controls",
                              "new-window-button",
                              "privatebrowsing-button",
                              "save-page-button",
                              "zoom-controls",

--- a/browser/components/customizableui/test/browser_884402_customize_from_overflow.js
+++ b/browser/components/customizableui/test/browser_884402_customize_from_overflow.js
@@ -8,16 +8,17 @@ var originalWindowWidth;
 registerCleanupFunction(function() {
   overflowPanel.removeAttribute("animate");
   window.resizeTo(originalWindowWidth, window.outerHeight);
 });
 
 // Right-click on an item within the overflow panel should
 // show a context menu with options to move it.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
 
   overflowPanel.setAttribute("animate", "false");
 
   originalWindowWidth = window.outerWidth;
   let navbar = document.getElementById(CustomizableUI.AREA_NAVBAR);
   ok(!navbar.hasAttribute("overflowing"), "Should start with a non-overflowing toolbar.");
   window.resizeTo(400, window.outerHeight);
 

--- a/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js
+++ b/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js
@@ -6,16 +6,17 @@
 
 function isFullscreenSizeMode() {
   let sizemode = document.documentElement.getAttribute("sizemode");
   return sizemode == "fullscreen";
 }
 
 // Observers should be disabled when in customization mode.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   // Open and close the panel to make sure that the
   // area is generated before getting a child of the area.
   let shownPanelPromise = promisePanelShown(window);
   PanelUI.toggle({type: "command"});
   yield shownPanelPromise;
   let hiddenPanelPromise = promisePanelHidden(window);
   PanelUI.toggle({type: "command"});
   yield hiddenPanelPromise;

--- a/browser/components/customizableui/test/browser_890140_orphaned_placeholders.js
+++ b/browser/components/customizableui/test/browser_890140_orphaned_placeholders.js
@@ -3,16 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 requestLongerTimeout(2);
 
 // One orphaned item should have two placeholders next to it.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
 
   if (isInDevEdition()) {
     CustomizableUI.addWidgetToArea("developer-button", CustomizableUI.AREA_PANEL);
     ok(!CustomizableUI.inDefaultState, "Should no longer be in default state.");
   }
   if (!isInDevEdition()) {
     ok(CustomizableUI.inDefaultState, "Should be in default state.");

--- a/browser/components/customizableui/test/browser_901207_searchbar_in_panel.js
+++ b/browser/components/customizableui/test/browser_901207_searchbar_in_panel.js
@@ -11,16 +11,17 @@ function* waitForSearchBarFocus() {
   yield waitForCondition(function() {
     logActiveElement();
     return document.activeElement === searchbar.textbox.inputField;
   });
 }
 
 // Ctrl+K should open the menu panel and focus the search bar if the search bar is in the panel.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let searchbar = document.getElementById("searchbar");
   gCustomizeMode.addToPanel(searchbar);
   let placement = CustomizableUI.getPlacementOfWidget("search-container");
   is(placement.area, CustomizableUI.AREA_PANEL, "Should be in panel");
 
   let shownPanelPromise = promisePanelShown(window);
   sendWebSearchKeyCommand();
   yield shownPanelPromise;

--- a/browser/components/customizableui/test/browser_914863_disabled_help_quit_buttons.js
+++ b/browser/components/customizableui/test/browser_914863_disabled_help_quit_buttons.js
@@ -1,14 +1,15 @@
 /* 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/. */
 
 // Entering then exiting customization mode should reenable the Help and Exit buttons.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   let helpButton = document.getElementById("PanelUI-help");
   let quitButton = document.getElementById("PanelUI-quit");
   ok(helpButton.getAttribute("disabled") == "true", "Help button should be disabled while in customization mode.");
   ok(quitButton.getAttribute("disabled") == "true", "Quit button should be disabled while in customization mode.");
   yield endCustomizing();
 
   ok(!helpButton.hasAttribute("disabled"), "Help button should not be disabled.");

--- a/browser/components/customizableui/test/browser_938995_indefaultstate_nonremovable.js
+++ b/browser/components/customizableui/test/browser_938995_indefaultstate_nonremovable.js
@@ -2,17 +2,19 @@
  * 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-non-removable-widget";
 
 // Adding non-removable items to a toolbar or the panel shouldn't change inDefaultState
-add_task(function() {
+add_task(async function() {
+  await SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
+  await PanelUI.ensureReady();
   ok(CustomizableUI.inDefaultState, "Should start in default state");
 
   let button = createDummyXULButton(kWidgetId, "Test non-removable inDefaultState handling");
   CustomizableUI.addWidgetToArea(kWidgetId, CustomizableUI.AREA_NAVBAR);
   button.setAttribute("removable", "false");
   ok(CustomizableUI.inDefaultState, "Should still be in default state after navbar addition");
   button.remove();
 

--- a/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
+++ b/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
@@ -2,16 +2,17 @@
  * 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 button, menuButton;
 /* Clicking a button should close the panel */
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   button = document.createElement("toolbarbutton");
   button.id = "browser_940307_button";
   button.setAttribute("label", "Button");
   PanelUI.contents.appendChild(button);
   yield PanelUI.show();
   let hiddenAgain = promisePanelHidden(window);
   EventUtils.synthesizeMouseAtCenter(button, {});
   yield hiddenAgain;

--- a/browser/components/customizableui/test/browser_947914_button_addons.js
+++ b/browser/components/customizableui/test/browser_947914_button_addons.js
@@ -3,16 +3,17 @@
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 var initialLocation = gBrowser.currentURI.spec;
 var newTab = null;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check addons button existence and functionality");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let addonsButton = document.getElementById("add-ons-button");
   ok(addonsButton, "Add-ons button exists in Panel Menu");
   addonsButton.click();

--- a/browser/components/customizableui/test/browser_947914_button_copy.js
+++ b/browser/components/customizableui/test/browser_947914_button_copy.js
@@ -3,16 +3,17 @@
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 var initialLocation = gBrowser.currentURI.spec;
 var globalClipboard;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield BrowserTestUtils.withNewTab({gBrowser, url: "about:blank"}, function*() {
     info("Check copy button existence and functionality");
 
     let testText = "copy text test";
 
     gURLBar.focus();
     info("The URL bar was focused");
     yield PanelUI.show();

--- a/browser/components/customizableui/test/browser_947914_button_cut.js
+++ b/browser/components/customizableui/test/browser_947914_button_cut.js
@@ -3,16 +3,17 @@
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 var initialLocation = gBrowser.currentURI.spec;
 var globalClipboard;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield BrowserTestUtils.withNewTab({gBrowser, url: "about:blank"}, function*() {
     info("Check cut button existence and functionality");
 
     let testText = "cut text test";
 
     gURLBar.focus();
     yield PanelUI.show();
     info("Menu panel was opened");

--- a/browser/components/customizableui/test/browser_947914_button_find.js
+++ b/browser/components/customizableui/test/browser_947914_button_find.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check find button existence and functionality");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let findButton = document.getElementById("find-button");
   ok(findButton, "Find button exists in Panel Menu");
 

--- a/browser/components/customizableui/test/browser_947914_button_history.js
+++ b/browser/components/customizableui/test/browser_947914_button_history.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check history button existence and functionality");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let historyButton = document.getElementById("history-panelmenu");
   ok(historyButton, "History button appears in Panel Menu");
 

--- a/browser/components/customizableui/test/browser_947914_button_newPrivateWindow.js
+++ b/browser/components/customizableui/test/browser_947914_button_newPrivateWindow.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check private browsing button existence and functionality");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let windowWasHandled = false;
   let privateWindow = null;
 

--- a/browser/components/customizableui/test/browser_947914_button_newWindow.js
+++ b/browser/components/customizableui/test/browser_947914_button_newWindow.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check new window button existence and functionality");
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let windowWasHandled = false;
   let newWindow = null;
 
   let observerWindowOpened = {

--- a/browser/components/customizableui/test/browser_947914_button_paste.js
+++ b/browser/components/customizableui/test/browser_947914_button_paste.js
@@ -3,16 +3,17 @@
   * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 var initialLocation = gBrowser.currentURI.spec;
 var globalClipboard;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield BrowserTestUtils.withNewTab({gBrowser, url: "about:blank"}, function*() {
     info("Check paste button existence and functionality");
 
     let clipboard = Cc["@mozilla.org/widget/clipboardhelper;1"].getService(Ci.nsIClipboardHelper);
     globalClipboard = Services.clipboard.kGlobalClipboard;
 
     yield PanelUI.show();
     info("Menu panel was opened");

--- a/browser/components/customizableui/test/browser_947914_button_print.js
+++ b/browser/components/customizableui/test/browser_947914_button_print.js
@@ -2,16 +2,17 @@
   * 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 isOSX = (Services.appinfo.OS === "Darwin");
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield BrowserTestUtils.withNewTab({
     gBrowser,
     url: "http://example.com/",
   }, function* () {
     info("Check print button existence and functionality");
 
     yield PanelUI.show();
     info("Menu panel was opened");

--- a/browser/components/customizableui/test/browser_947914_button_savePage.js
+++ b/browser/components/customizableui/test/browser_947914_button_savePage.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check save page button existence");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let savePageButton = document.getElementById("save-page-button");
   ok(savePageButton, "Save Page button exists in Panel Menu");
 

--- a/browser/components/customizableui/test/browser_947914_button_zoomIn.js
+++ b/browser/components/customizableui/test/browser_947914_button_zoomIn.js
@@ -2,16 +2,17 @@
   * 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 initialPageZoom = ZoomManager.zoom;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check zoom in button existence and functionality");
 
   is(initialPageZoom, 1, "Initial zoom factor should be 1");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let zoomInButton = document.getElementById("zoom-in-button");

--- a/browser/components/customizableui/test/browser_947914_button_zoomOut.js
+++ b/browser/components/customizableui/test/browser_947914_button_zoomOut.js
@@ -2,16 +2,17 @@
   * 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 initialPageZoom = ZoomManager.zoom;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check zoom out button existence and functionality");
 
   is(initialPageZoom, 1, "Initial zoom factor should be 1");
 
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let zoomOutButton = document.getElementById("zoom-out-button");

--- a/browser/components/customizableui/test/browser_947914_button_zoomReset.js
+++ b/browser/components/customizableui/test/browser_947914_button_zoomReset.js
@@ -2,16 +2,17 @@
   * 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 initialPageZoom = ZoomManager.zoom;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check zoom reset button existence and functionality");
 
   is(initialPageZoom, 1, "Page zoom reset correctly");
   ZoomManager.zoom = 0.5;
   yield PanelUI.show();
   info("Menu panel was opened");
 
   let zoomResetButton = document.getElementById("zoom-reset-button");

--- a/browser/components/customizableui/test/browser_962884_opt_in_disable_hyphens.js
+++ b/browser/components/customizableui/test/browser_962884_opt_in_disable_hyphens.js
@@ -1,15 +1,16 @@
 /* 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";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   const kNormalLabel = "Character Encoding";
   CustomizableUI.addWidgetToArea("characterencoding-button", CustomizableUI.AREA_NAVBAR);
   let characterEncoding = document.getElementById("characterencoding-button");
   const kOriginalLabel = characterEncoding.getAttribute("label");
   characterEncoding.setAttribute("label", "\u00ad" + kNormalLabel);
   CustomizableUI.addWidgetToArea("characterencoding-button", CustomizableUI.AREA_PANEL);
 
   yield PanelUI.show();

--- a/browser/components/customizableui/test/browser_967000_button_charEncoding.js
+++ b/browser/components/customizableui/test/browser_967000_button_charEncoding.js
@@ -2,16 +2,17 @@
  * 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 TEST_PAGE = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/test_967000_charEncoding_page.html";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check Character Encoding button functionality");
 
   // add the Character Encoding button to the panel
   CustomizableUI.addWidgetToArea("characterencoding-button",
                                   CustomizableUI.AREA_PANEL);
 
   // check the button's functionality
   yield PanelUI.show();

--- a/browser/components/customizableui/test/browser_967000_button_feeds.js
+++ b/browser/components/customizableui/test/browser_967000_button_feeds.js
@@ -6,16 +6,17 @@
 
 const TEST_PAGE = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/feeds_test_page.html";
 const TEST_FEED = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/test-feed.xml"
 
 var newTab = null;
 var initialLocation = gBrowser.currentURI.spec;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check Subscribe button functionality");
 
   // add the Subscribe button to the panel
   CustomizableUI.addWidgetToArea("feed-button",
                                   CustomizableUI.AREA_PANEL);
 
   // check the button's functionality
   yield PanelUI.show();

--- a/browser/components/customizableui/test/browser_968447_bookmarks_toolbar_items_in_panel.js
+++ b/browser/components/customizableui/test/browser_968447_bookmarks_toolbar_items_in_panel.js
@@ -2,16 +2,17 @@
  * 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";
 
 // Bug 968447 - The Bookmarks Toolbar Items doesn't appear as a
 // normal menu panel button in new windows.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   const buttonId = "bookmarks-toolbar-placeholder";
   yield startCustomizing();
   CustomizableUI.addWidgetToArea("personal-bookmarks", CustomizableUI.AREA_PANEL);
   yield endCustomizing();
 
   yield PanelUI.show();
 
   let bookmarksToolbarPlaceholder = document.getElementById(buttonId);

--- a/browser/components/customizableui/test/browser_969661_character_encoding_navbar_disabled.js
+++ b/browser/components/customizableui/test/browser_969661_character_encoding_navbar_disabled.js
@@ -3,16 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 
 // Adding the character encoding menu to the panel, exiting customize mode,
 // and moving it to the nav-bar should have it enabled, not disabled.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   yield startCustomizing();
   CustomizableUI.addWidgetToArea("characterencoding-button", "PanelUI-contents");
   yield endCustomizing();
   yield PanelUI.show();
   let panelHiddenPromise = promisePanelHidden(window);
   PanelUI.hide();
   yield panelHiddenPromise;
   CustomizableUI.addWidgetToArea("characterencoding-button", "nav-bar");

--- a/browser/components/customizableui/test/browser_970511_undo_restore_default.js
+++ b/browser/components/customizableui/test/browser_970511_undo_restore_default.js
@@ -3,16 +3,17 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 requestLongerTimeout(2);
 
 // Restoring default should reset theme and show an "undo" option which undoes the restoring operation.
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let homeButtonId = "home-button";
   CustomizableUI.removeWidgetFromArea(homeButtonId);
   yield startCustomizing();
   ok(!CustomizableUI.inDefaultState, "Not in default state to begin with");
   is(CustomizableUI.getPlacementOfWidget(homeButtonId), null, "Home button is in palette");
   let undoResetButton = document.getElementById("customization-undo-reset-button");
   is(undoResetButton.hidden, true, "The undo button is hidden before reset");
 

--- a/browser/components/customizableui/test/browser_972267_customizationchange_events.js
+++ b/browser/components/customizableui/test/browser_972267_customizationchange_events.js
@@ -2,16 +2,17 @@
  * 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";
 
 // Create a new window, then move the home button to the menu and check both windows have
 // customizationchange events fire on the toolbox:
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let newWindow = yield openAndLoadWindow();
   let otherToolbox = newWindow.gNavToolbox;
 
   let handlerCalledCount = 0;
   let handler = (ev) => {
     handlerCalledCount++;
   };
 

--- a/browser/components/customizableui/test/browser_973641_button_addon.js
+++ b/browser/components/customizableui/test/browser_973641_button_addon.js
@@ -3,16 +3,18 @@
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 "use strict";
 
 const kButton = "test_button_for_addon";
 var initialLocation = gBrowser.currentURI.spec;
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
+
   info("Check addon button functionality");
 
   // create mocked addon button on the navigation bar
   let widgetSpec = {
     id: kButton,
     type: "button",
     onClick() {
       gBrowser.selectedTab = gBrowser.addTab("about:addons");

--- a/browser/components/customizableui/test/browser_981305_separator_insertion.js
+++ b/browser/components/customizableui/test/browser_981305_separator_insertion.js
@@ -57,16 +57,20 @@ function checkSeparatorInsertion(menuId,
     yield panelHiddenPromise;
 
     if (changedPlacement) {
       CustomizableUI.reset();
     }
   };
 }
 
+add_task(async function () {
+  await SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
+});
+
 add_task(checkSeparatorInsertion("menuWebDeveloperPopup", "developer-button", "PanelUI-developerItems"));
 add_task(checkSeparatorInsertion("viewSidebarMenu", "sidebar-button", "PanelUI-sidebarItems"));
 
 registerCleanupFunction(function() {
   for (let el of tempElements) {
     el.remove();
   }
   tempElements = null;

--- a/browser/components/customizableui/test/browser_981418-widget-onbeforecreated-handler.js
+++ b/browser/components/customizableui/test/browser_981418-widget-onbeforecreated-handler.js
@@ -2,16 +2,17 @@
  * 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-981418-widget-onbeforecreated";
 
 // Should be able to add broken view widget
 add_task(function* testAddOnBeforeCreatedWidget() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let viewShownDeferred = Promise.defer();
   let onBeforeCreatedCalled = false;
   let widgetSpec = {
     id: kWidgetId,
     type: "view",
     viewId: kWidgetId + "idontexistyet",
     onBeforeCreated(doc) {
       let view = doc.createElement("panelview");

--- a/browser/components/customizableui/test/browser_984455_bookmarks_items_reparenting.js
+++ b/browser/components/customizableui/test/browser_984455_bookmarks_items_reparenting.js
@@ -185,16 +185,17 @@ function checkNotOverflowing(aID) {
      "Item with ID " + aID + " should not have overflowedItem attribute");
 }
 
 /**
  * Test that overflowing the bookmarks menu button doesn't break the
  * context menus for the Unsorted and Bookmarks Toolbar menu items.
  */
 add_task(function* testOverflowingBookmarksButtonContextMenu() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   ok(!gNavBar.hasAttribute("overflowing"), "Should start with a non-overflowing toolbar.");
   ok(CustomizableUI.inDefaultState, "Should start in default state.");
 
   // Open the Unsorted and Bookmarks Toolbar context menus and ensure
   // that they have views attached.
   yield checkSpecialContextMenus();
 
   yield overflowEverything();

--- a/browser/components/customizableui/test/browser_987640_charEncoding.js
+++ b/browser/components/customizableui/test/browser_987640_charEncoding.js
@@ -2,16 +2,17 @@
  * 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 TEST_PAGE = "http://mochi.test:8888/browser/browser/components/customizableui/test/support/test_967000_charEncoding_page.html";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Check Character Encoding panel functionality");
 
   // add the Character Encoding button to the panel
   CustomizableUI.addWidgetToArea("characterencoding-button",
                                   CustomizableUI.AREA_PANEL);
 
   let newTab = yield BrowserTestUtils.openNewForegroundTab(gBrowser, TEST_PAGE, true, true);
 

--- a/browser/components/customizableui/test/browser_989751_subviewbutton_class.js
+++ b/browser/components/customizableui/test/browser_989751_subviewbutton_class.js
@@ -47,16 +47,19 @@ function checkSubviewButtonClass(menuId,
     PanelUI.hide();
     yield panelHiddenPromise;
 
     if (changedPlacement) {
       CustomizableUI.reset();
     }
   };
 }
+add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
+});
 
 add_task(checkSubviewButtonClass("menuWebDeveloperPopup", "developer-button", "PanelUI-developerItems"));
 add_task(checkSubviewButtonClass("viewSidebarMenu", "sidebar-button", "PanelUI-sidebarItems"));
 
 registerCleanupFunction(function() {
   tempElement.classList.remove(kCustomClass)
   tempElement = null;
 });

--- a/browser/components/customizableui/test/browser_customizemode_contextmenu_menubuttonstate.js
+++ b/browser/components/customizableui/test/browser_customizemode_contextmenu_menubuttonstate.js
@@ -1,11 +1,12 @@
 "use strict";
 
 add_task(function*() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   ok(!PanelUI.menuButton.hasAttribute("open"), "Menu button should not be 'pressed' outside customize mode");
   yield startCustomizing();
 
   is(PanelUI.menuButton.getAttribute("open"), "true", "Menu button should be 'pressed' when in customize mode");
 
   let contextMenu = document.getElementById("customizationPanelItemContextMenu");
   let shownPromise = popupShown(contextMenu);
   let newWindowButton = document.getElementById("wrapper-new-window-button");

--- a/browser/components/customizableui/test/browser_remote_tabs_button.js
+++ b/browser/components/customizableui/test/browser_remote_tabs_button.js
@@ -10,16 +10,17 @@ const service = syncService.Service;
 Components.utils.import("resource://services-sync/UIState.jsm");
 
 let getState;
 let originalSync;
 let syncWasCalled = false;
 
 // TODO: This test should probably be re-written, we don't really test much here.
 add_task(async function testSyncRemoteTabsButtonFunctionality() {
+  await SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   info("Test the Sync Remote Tabs button in the PanelUI");
   storeInitialValues();
   mockFunctions();
 
   // Force UI update.
   Services.obs.notifyObservers(null, UIState.ON_UPDATE);
 
   // add the sync remote tabs button to the panel

--- a/browser/components/customizableui/test/browser_synced_tabs_menu.js
+++ b/browser/components/customizableui/test/browser_synced_tabs_menu.js
@@ -34,16 +34,17 @@ let mockedInternal = {
   get isConfiguredToSyncTabs() { return true; },
   getTabClients() { return Promise.resolve([]); },
   syncTabs() { return Promise.resolve(); },
   hasSyncedThisSession: false,
 };
 
 
 add_task(function* setup() {
+  yield SpecialPowers.pushPrefEnv({set: [["browser.photon.structure.enabled", false]]});
   let oldInternal = SyncedTabs._internal;
   SyncedTabs._internal = mockedInternal;
 
   // This test hacks some observer states to simulate a user being signed
   // in to Sync - restore them when the test completes.
   let initialObserverStates = {};
   for (let id of ["sync-reauth-state", "sync-setup-state", "sync-syncnow-state"]) {
     initialObserverStates[id] = document.getElementById(id).hidden;