Merge "Ensure window has been added in isTopOfTask" into nyc-dev

am: e6ef0f9

* commit 'e6ef0f9d77efdd5852ac2e3d768280dc3571dcf7':
  Ensure window has been added in isTopOfTask

Change-Id: I16c17d62a344f4fcf71b817ab2228b13261aae7e

core/java/android/app/Activity.java

@@ -5920,6 +5920,9 @@ public class Activity extends ContextThemeWrapper
      * @return true if this is the topmost, non-finishing activity in its task.
      */
     private boolean isTopOfTask() {
+        if (mToken == null || mWindow == null || !mWindowAdded) {
+            return false;
+        }
         try {
             return ActivityManagerNative.getDefault().isTopOfTask(mToken);
         } catch (RemoteException e) {