diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_885052_customize_mode_observers_disabed.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,39 @@
+/* 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";
+
+// Observers should be disabled when in customization mode.
+add_task(function() {
+  // 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;
+
+  let fullscreenButton = document.getElementById("fullscreen-button");
+  ok(!fullscreenButton.checked, "Fullscreen button should not be checked when not in fullscreen.")
+
+  BrowserFullScreen();
+  yield waitForCondition(function() fullscreenButton.checked);
+  ok(fullscreenButton.checked, "Fullscreen button should be checked when in fullscreen.")
+
+  yield startCustomizing();
+
+  let fullscreenButtonWrapper = document.getElementById("wrapper-fullscreen-button");
+  ok(fullscreenButtonWrapper.hasAttribute("itemobserves"), "Observer should be moved to wrapper");
+  fullscreenButton = document.getElementById("fullscreen-button");
+  ok(!fullscreenButton.hasAttribute("observes"), "Observer should be removed from button");
+  ok(!fullscreenButton.checked, "Fullscreen button should no longer be checked during customization mode");
+
+  yield endCustomizing();
+
+  BrowserFullScreen();
+  fullscreenButton = document.getElementById("fullscreen-button");
+  yield waitForCondition(function() !fullscreenButton.checked);
+  ok(!fullscreenButton.checked, "Fullscreen button should not be checked when not in fullscreen.")
+});