Bug 676410 - Exception in isKeyboardOpened when called from local page [r=wesj]

mobile/chrome/content/Util.js

@@ -183,7 +183,9 @@ let Util = {
   },
 
   get isKeyboardOpened() {
-    let isChromeWindow = this.isParentProcess() && window["ViewableAreaObserver"];
+    // This might get called from the child process, or from a frame script in the
+    // parent process (which does not have access to the main "window" global).
+    let isChromeWindow = this.isParentProcess() && typeof window == "object" && window["ViewableAreaObserver"];
     if (isChromeWindow)
       return ViewableAreaObserver.isKeyboardOpened;