Fix handling of tab contents disappearing out from underneath Javascript dialogs.

chrome/browser/ui/app_modal_dialogs/message_box_handler.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/ui/app_modal_dialogs/message_box_handler.h"
 
 #include <map>
 
 #include "base/compiler_specific.h"
 #include "base/memory/singleton.h"
@@ skipping 156 matching lines @@
       break;
     }
   }
   NOTREACHED();
   return string16();
 }
 
 void ChromeJavaScriptDialogCreator::CancelPendingDialogs(
     content::DialogDelegate* delegate) {
   AppModalDialogQueue* queue = AppModalDialogQueue::GetInstance();
+  AppModalDialog* active_dialog = queue->active_dialog();
+  if (active_dialog && active_dialog->delegate() == delegate)
+    active_dialog->Invalidate();
   for (AppModalDialogQueue::iterator i = queue->begin();
        i != queue->end(); ++i) {
     if ((*i)->delegate() == delegate)
       (*i)->Invalidate();
   }
 }
 
 //------------------------------------------------------------------------------
 
 content::JavaScriptDialogCreator* GetJavaScriptDialogCreatorInstance() {
   return ChromeJavaScriptDialogCreator::GetInstance();
 }