Add support for BeforeUnloadEvent

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 2323 matching lines @@
         return true;
 
     RefPtr<Document> protect(this);
 
     RefPtr<BeforeUnloadEvent> beforeUnloadEvent = BeforeUnloadEvent::create();
     m_loadEventProgress = BeforeUnloadEventInProgress;
     dispatchWindowEvent(beforeUnloadEvent.get(), this);
     m_loadEventProgress = BeforeUnloadEventCompleted;
     if (!beforeUnloadEvent->defaultPrevented())
         defaultEventHandler(beforeUnloadEvent.get());
-    if (beforeUnloadEvent->result().isNull())
+    if (beforeUnloadEvent->returnValue().isNull())
         return true;
 
     if (navigatingDocument->m_didAllowNavigationViaBeforeUnloadConfirmationPanel) {
         addConsoleMessage(JSMessageSource, ErrorMessageLevel, "Blocked attempt to show multiple 'beforeunload' confirmation panels for a single navigation.");
         return true;
     }
 
-    String text = displayStringModifiedByEncoding(beforeUnloadEvent->result());
+    String text = displayStringModifiedByEncoding(beforeUnloadEvent->returnValue());
     if (chrome.runBeforeUnloadConfirmPanel(text, m_frame)) {
         navigatingDocument->m_didAllowNavigationViaBeforeUnloadConfirmationPanel = true;
         return true;
     }
     return false;
 }
 
 void Document::dispatchUnloadEvents()
 {
     RefPtr<Document> protect(this);
@@ skipping 2931 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore