diff -r 000000000000 -r 6474c204b198 layout/base/tests/browser_bug617076.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/base/tests/browser_bug617076.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,61 @@
+function test()
+{
+  waitForExplicitFinish();
+
+  test1();
+}
+
+/**
+ * 1. load about:addons in a new tab and select that tab
+ * 2. insert a button with tooltiptext
+ * 3. create a new blank tab and select that tab
+ * 4. select the about:addons tab and hover the inserted button
+ * 5. remove the about:addons tab
+ * 6. remove the blank tab
+ *
+ * the test succeeds if it doesn't trigger any assertions
+ */
+function test1() {
+  let uri = "about:addons";
+  let tab = gBrowser.addTab();
+
+  tab.linkedBrowser.addEventListener("load", function(aEvent) {
+    tab.linkedBrowser.removeEventListener("load", arguments.callee, true);
+
+    let doc = gBrowser.contentDocument;
+    var e = doc.createElement("button");
+    e.setAttribute('label', "hello");
+    e.setAttribute('tooltiptext', "world");
+    doc.documentElement.insertBefore(e, doc.documentElement.firstChild);
+
+    let tab2 = gBrowser.addTab();
+    gBrowser.selectedTab = tab2;
+
+    setTimeout(function() {
+      gBrowser.selectedTab = tab;
+
+      let doc = gBrowser.contentDocument;
+      var win = gBrowser.contentWindow;
+      EventUtils.disableNonTestMouseEvents(true);
+      try {
+        EventUtils.synthesizeMouse(e, 1, 1, { type: "mouseover" }, win);
+        EventUtils.synthesizeMouse(e, 2, 6, { type: "mousemove" }, win);
+        EventUtils.synthesizeMouse(e, 2, 4, { type: "mousemove" }, win);
+      } finally {
+        EventUtils.disableNonTestMouseEvents(false);
+      }
+
+      executeSoon(function() {
+        gBrowser.removeTab(tab, {animate: false});
+        gBrowser.removeTab(tab2, {animate: false});
+        ok(true, "pass if no assertions");
+
+        // done
+        executeSoon(finish);
+      });
+    }, 0);
+  }, true);
+
+  gBrowser.selectedTab = tab;
+  gBrowser.selectedTab.linkedBrowser.loadURI(uri);
+}