diff -r 000000000000 -r 6474c204b198 browser/base/content/test/general/browser_bug419612.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/base/content/test/general/browser_bug419612.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,32 @@
+function test() {
+  waitForExplicitFinish();
+
+  Task.spawn(function () {
+    let testPage = "http://example.org/browser/browser/base/content/test/general/dummy_page.html";
+    let tab1 = gBrowser.addTab();
+    yield FullZoomHelper.selectTabAndWaitForLocationChange(tab1);
+    yield FullZoomHelper.load(tab1, testPage);
+
+    let tab2 = gBrowser.addTab();
+    yield FullZoomHelper.load(tab2, testPage);
+
+    FullZoom.enlarge();
+    let tab1Zoom = ZoomManager.getZoomForBrowser(tab1.linkedBrowser);
+
+    yield FullZoomHelper.selectTabAndWaitForLocationChange(tab2);
+    let tab2Zoom = ZoomManager.getZoomForBrowser(tab2.linkedBrowser);
+    is(tab2Zoom, tab1Zoom, "Zoom should affect background tabs");
+
+    gPrefService.setBoolPref("browser.zoom.updateBackgroundTabs", false);
+    FullZoom.reset();
+    gBrowser.selectedTab = tab1;
+    tab1Zoom = ZoomManager.getZoomForBrowser(tab1.linkedBrowser);
+    tab2Zoom = ZoomManager.getZoomForBrowser(tab2.linkedBrowser);
+    isnot(tab1Zoom, tab2Zoom, "Zoom should not affect background tabs");
+
+    if (gPrefService.prefHasUserValue("browser.zoom.updateBackgroundTabs"))
+      gPrefService.clearUserPref("browser.zoom.updateBackgroundTabs");
+    yield FullZoomHelper.removeTabAndWaitForLocationChange(tab1);
+    yield FullZoomHelper.removeTabAndWaitForLocationChange(tab2);
+  }).then(finish, FullZoomHelper.failAndContinue(finish));
+}