Have HTMLCollection::item() return an Element as per specification

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 459 matching lines @@
     if (!m_recursiveSerialization)
         return;
     // Collect all frames inside the specified frame.
     for (int i = 0; i < static_cast<int>(m_frames.size()); ++i) {
         WebFrameImpl* currentFrame = m_frames[i];
         // Get current using document.
         Document* currentDoc = currentFrame->frame()->document();
         // Go through sub-frames.
         RefPtr<HTMLCollection> all = currentDoc->all();
 
-        for (unsigned i = 0; Node* node = all->item(i); i++) {
-            if (!node->isHTMLElement())
+        for (unsigned i = 0; Element* element = all->item(i); i++) {
+            if (!element->isHTMLElement())
                 continue;
-            Element* element = toElement(node);
             WebFrameImpl* webFrame =
                 WebFrameImpl::fromFrameOwnerElement(element);
             if (webFrame)
                 m_frames.append(webFrame);
         }
     }
 }
 
 bool WebPageSerializerImpl::serialize()
 {
@@ skipping 24 matching lines @@
 
         encodeAndFlushBuffer(WebPageSerializerClient::CurrentFrameIsFinished, &param, ForceFlush);
     }
 
     ASSERT(m_dataBuffer.isEmpty());
     m_client->didSerializeDataForFrame(KURL(), WebCString("", 0), WebPageSerializerClient::AllFramesAreFinished);
     return didSerialization;
 }
 
 }  // namespace blink