diff -r 000000000000 -r 6474c204b198 browser/components/customizableui/test/browser_934951_zoom_in_toolbar.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/components/customizableui/test/browser_934951_zoom_in_toolbar.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,82 @@
+/* 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 kTimeoutInMS = 20000;
+
+// Bug 934951 - Zoom controls percentage label doesn't update when it's in the toolbar and you navigate.
+add_task(function() {
+  CustomizableUI.addWidgetToArea("zoom-controls", CustomizableUI.AREA_NAVBAR);
+  let tab1 = gBrowser.addTab("about:mozilla");
+  let tab2 = gBrowser.addTab("about:newtab");
+  gBrowser.selectedTab = tab1;
+  let zoomResetButton = document.getElementById("zoom-reset-button");
+
+  registerCleanupFunction(() => {
+    info("Cleaning up.");
+    CustomizableUI.reset();
+    gBrowser.removeTab(tab2);
+    gBrowser.removeTab(tab1);
+  });
+
+  is(parseInt(zoomResetButton.label, 10), 100, "Default zoom is 100% for about:mozilla");
+  let zoomChangePromise = promiseObserverNotification("browser-fullZoom:zoomChange");
+  FullZoom.enlarge();
+  yield zoomChangePromise;
+  is(parseInt(zoomResetButton.label, 10), 110, "Zoom is changed to 110% for about:mozilla");
+
+  let tabSelectPromise = promiseTabSelect();
+  gBrowser.selectedTab = tab2;
+  yield tabSelectPromise;
+  is(parseInt(zoomResetButton.label, 10), 100, "Default zoom is 100% for about:newtab");
+
+  gBrowser.selectedTab = tab1;
+  let zoomResetPromise = promiseObserverNotification("browser-fullZoom:zoomReset");
+  FullZoom.reset();
+  yield zoomResetPromise;
+  is(parseInt(zoomResetButton.label, 10), 100, "Default zoom is 100% for about:mozilla");
+
+  // Test zoom label updates while navigating pages in the same tab.
+  FullZoom.enlarge();
+  yield zoomChangePromise;
+  is(parseInt(zoomResetButton.label, 10), 110, "Zoom is changed to 110% for about:mozilla");
+  yield promiseTabLoadEvent(tab1, "about:home");
+  is(parseInt(zoomResetButton.label, 10), 100, "Default zoom is 100% for about:home");
+  yield promiseTabHistoryNavigation(-1, function() {
+    return parseInt(zoomResetButton.label, 10) == 110;
+  });
+  is(parseInt(zoomResetButton.label, 10), 110, "Zoom is still 110% for about:mozilla");
+});
+
+function promiseObserverNotification(aObserver) {
+  let deferred = Promise.defer();
+  function notificationCallback(e) {
+    Services.obs.removeObserver(notificationCallback, aObserver, false);
+    clearTimeout(timeoutId);
+    deferred.resolve();
+  };
+  let timeoutId = setTimeout(() => {
+    Services.obs.removeObserver(notificationCallback, aObserver, false);
+    deferred.reject("Notification '" + aObserver + "' did not happen within 20 seconds.");
+  }, kTimeoutInMS);
+  Services.obs.addObserver(notificationCallback, aObserver, false);
+  return deferred.promise;
+}
+
+function promiseTabSelect() {
+  let deferred = Promise.defer();
+  let container = window.gBrowser.tabContainer;
+  let timeoutId = setTimeout(() => {
+    container.removeEventListener("TabSelect", callback);
+    deferred.reject("TabSelect did not happen within 20 seconds");
+  }, kTimeoutInMS);
+  function callback(e) {
+    container.removeEventListener("TabSelect", callback);
+    clearTimeout(timeoutId);
+    executeSoon(deferred.resolve);
+  };
+  container.addEventListener("TabSelect", callback);
+  return deferred.promise;
+}