Introduce isHTMLHtmlElement and toHTMLHtmlElement

Source/core/html/PluginDocument.cpp

 /*
  * Copyright (C) 2006, 2008 Apple 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.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 54 matching lines @@
 
     PluginView* pluginView() const;
 
     HTMLEmbedElement* m_embedElement;
 };
 
 void PluginDocumentParser::createDocumentStructure()
 {
     RefPtr<Element> rootElement = document()->createElement(htmlTag, false);
     document()->appendChild(rootElement, IGNORE_EXCEPTION);
-    static_cast<HTMLHtmlElement*>(rootElement.get())->insertedByParser();
+    toHTMLHtmlElement(rootElement.get())->insertedByParser();
 
     if (document()->frame() && document()->frame()->loader())
         document()->frame()->loader()->dispatchDocumentElementAvailable();
 
     RefPtr<Element> body = document()->createElement(bodyTag, false);
     body->setAttribute(marginwidthAttr, "0");
     body->setAttribute(marginheightAttr, "0");
     body->setAttribute(styleAttr, "background-color: rgb(38,38,38)");
 
     rootElement->appendChild(body, IGNORE_EXCEPTION);
@@ skipping 110 matching lines @@
     // with how many times we call beforeload on object elements. <rdar://problem/8441094>.
     if (!shouldLoadPluginManually())
         return;
 
     DocumentLoader* documentLoader = frame()->loader()->activeDocumentLoader();
     documentLoader->cancelMainResourceLoad(frame()->loader()->cancelledError(documentLoader->request()));
     setShouldLoadPluginManually(false);
 }
 
 }