Refactoring: Introduce ResouceLoaderHost interface for unloading ResourceLoader.

Source/core/loader/DocumentLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer. 
@@ skipping 289 matching lines @@
     if (document() && document()->hasActiveParser())
         return true;
 
     return isLoadingMainResource() || !m_resourceLoaders.isEmpty();
 }
 
 void DocumentLoader::notifyFinished(CachedResource* resource)
 {
     ASSERT_UNUSED(resource, m_mainResource == resource);
     ASSERT(m_mainResource);
+
+    RefPtr<DocumentLoader> protect(this);
+
     if (!m_mainResource->errorOccurred() && !m_mainResource->wasCanceled()) {
         finishedLoading(m_mainResource->loadFinishTime());
         return;
     }
 
     mainReceivedError(m_mainResource->resourceError());
 }
 
 void DocumentLoader::finishedLoading(double finishTime)
 {
@@ skipping 577 matching lines @@
 const KURL& DocumentLoader::unreachableURL() const
 {
     return m_substituteData.failingURL();
 }
 
 void DocumentLoader::setDefersLoading(bool defers)
 {
     // Multiple frames may be loading the same main resource simultaneously. If deferral state changes,
     // each frame's DocumentLoader will try to send a setDefersLoading() to the same underlying ResourceLoader. Ensure only
     // the "owning" DocumentLoader does so, as setDefersLoading() is not resilient to setting the same value repeatedly.
-    if (mainResourceLoader() && mainResourceLoader()->documentLoader() == this)
+    if (mainResourceLoader() && mainResourceLoader()->isLoadedBy(m_cachedResourceLoader.get()))
         mainResourceLoader()->setDefersLoading(defers);
 
     setAllDefersLoading(m_resourceLoaders, defers);
 }
 
 void DocumentLoader::stopLoadingSubresources()
 {
     cancelAll(m_resourceLoaders);
 }
 
@@ skipping 181 matching lines @@
 void DocumentLoader::replaceDocument(const String& source, Document* ownerDocument)
 {
     m_frame->loader()->stopAllLoaders();
     m_writer = createWriterFor(m_frame, ownerDocument, m_frame->document()->url(), mimeType(), m_writer ? m_writer->encoding() : "",  m_writer ? m_writer->encodingWasChosenByUser() : false, true);
     if (!source.isNull())
         m_writer->appendReplacingData(source);
     endWriting(m_writer.get());
 }
 
 } // namespace WebCore