Bug 499912, crash activating window with no root element, r+sr=smaug

dom/base/nsGlobalWindow.cpp

@@ -6654,11 +6654,13 @@ nsGlobalWindow::ActivateOrDeactivate(PRBool aActivate)
       nsCOMPtr<nsIDOMChromeWindow> chromeWin = do_QueryInterface(topLevelWindow);
       if (xulDoc && chromeWin) {
         nsCOMPtr<nsIContent> rootElem = doc->GetRootContent();
-        if (aActivate)
-          rootElem->SetAttr(kNameSpaceID_None, nsGkAtoms::active,
-                            NS_LITERAL_STRING("true"), PR_TRUE);
-        else
-          rootElem->UnsetAttr(kNameSpaceID_None, nsGkAtoms::active, PR_TRUE);
+        if (rootElem) {
+          if (aActivate)
+            rootElem->SetAttr(kNameSpaceID_None, nsGkAtoms::active,
+                              NS_LITERAL_STRING("true"), PR_TRUE);
+          else
+            rootElem->UnsetAttr(kNameSpaceID_None, nsGkAtoms::active, PR_TRUE);
+        }
       }
     }
   }

dom/tests/mochitest/chrome/window_focus.xul

@@ -1119,13 +1119,29 @@ function switchWindowTest(otherWindow, framesetWindow)
   otherWindow.close();
   framesetWindow.close();
 
+  gRefocusCallback = doWindowNoRootTest;
+}
+
+// open a window with no root element
+var noRootWindow = null;
+function doWindowNoRootTest()
+{
+  var data = "data:application/vnd.mozilla.xul+xml," + unescape(
+             "<window onfocus='dostuff()' xmlns='http://www.mozilla.org/keymaster/gatekeeper/there.is.only.xul'" +
+             "        style='-moz-user-focus: normal;'>" +
+             "<script>function dostuff() { setTimeout(function() { " +
+             "document.documentElement.focus(); document.removeChild(document.documentElement);" +
+             "window.opener.focus(); }, 100); }</script></window>");
+
   gRefocusCallback = doFrameSwitchingTests;
+  noRootWindow = window.open(data, "_blank", "chrome,width=100,height=100");
 }
 
 // these tests check when focus is moved between a tree of frames to ensure
 // that the focus is in the right place at each event step.
 function doFrameSwitchingTests()
 {
+  noRootWindow.close();
   gRefocusCallback = null;
 
   var framea = document.getElementById("ifa");