Refactoring: Simplify DocumentWriter by reorganizing its lifetime.

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 2123 matching lines @@
         return;
 
     // We have to clear the parser to avoid possibly triggering
     // the onload handler when closing as a side effect of a cancel-style
     // change, such as opening a new document or closing the window while
     // still parsing
     detachParser();
     explicitClose();
 }
 
-void Document::implicitOpen()
+PassRefPtr<DocumentParser> Document::implicitOpen()
 {
     cancelParsing();
 
     removeChildren();
     ASSERT(!m_focusedNode);
 
     setCompatibilityMode(NoQuirksMode);
 
     // Documents rendered seamlessly should start out requiring a stylesheet
     // collection update in order to ensure they inherit all the relevant data
     // from their parent.
     if (shouldDisplaySeamlesslyWithParent())
         styleResolverChanged(DeferRecalcStyle);
 
     m_parser = createParser();
     setParsing(true);
     setReadyState(Loading);
+
+    return m_parser;
 }
 
 HTMLElement* Document::body() const
 {
     Node* de = documentElement();
     if (!de)
         return 0;
 
     // try to prefer a FRAMESET element over BODY
     Node* body = 0;
@@ skipping 3037 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore