Refactoring: Add toWebFrameImpl() interface.

Source/web/WebPageSerializerImpl.cpp

 /*
  * Copyright (C) 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 428 matching lines @@
                                              const WebString& localDirectoryName)
     : m_client(client)
     , m_recursiveSerialization(recursiveSerialization)
     , m_framesCollected(false)
     , m_localDirectoryName(localDirectoryName)
     , m_htmlEntities(false)
     , m_xmlEntities(true)
 {
     // Must specify available webframe.
     ASSERT(frame);
-    m_specifiedWebFrameImpl = static_cast<WebFrameImpl*>(frame);
+    m_specifiedWebFrameImpl = toWebFrameImpl(frame);
     // Make sure we have non 0 client.
     ASSERT(client);
     // Build local resources map.
     ASSERT(links.size() == localPaths.size());
     for (size_t i = 0; i < links.size(); i++) {
         KURL url = links[i];
         ASSERT(!m_localLinks.contains(url.string()));
         m_localLinks.set(url.string(), localPaths[i]);
     }
 
@@ skipping 61 matching lines @@
 
         encodeAndFlushBuffer(WebPageSerializerClient::CurrentFrameIsFinished, &param, ForceFlush);
     }
 
     ASSERT(m_dataBuffer.isEmpty());
     m_client->didSerializeDataForFrame(KURL(), WebCString("", 0), WebPageSerializerClient::AllFramesAreFinished);
     return didSerialization;
 }
 
 }  // namespace WebKit