Use new is*Element() helper functions more in bindings/ code

Source/bindings/v8/V8WindowShell.cpp

 /*
  * Copyright (C) 2008, 2009, 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:
  *
  *     * 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 407 matching lines @@
 {
     if (!htmlDocument->hasNamedItem(key) && !htmlDocument->hasExtraNamedItem(key))
         return v8Undefined();
 
     RefPtr<HTMLCollection> items = htmlDocument->documentNamedItems(key);
     if (items->isEmpty())
         return v8Undefined();
 
     if (items->hasExactlyOneItem()) {
         Element* element = items->item(0);
+        ASSERT(element);
         LocalFrame* frame = 0;
-        if (element->hasTagName(HTMLNames::iframeTag) && (frame = toHTMLIFrameElement(element)->contentFrame()))
+        if (isHTMLIFrameElement(*element) && (frame = toHTMLIFrameElement(*element).contentFrame()))
             return toV8(frame->domWindow(), creationContext, isolate);
         return toV8(element, creationContext, isolate);
     }
     return toV8(items.release(), creationContext, isolate);
 }
 
 static void getter(v8::Local<v8::String> property, const v8::PropertyCallbackInfo<v8::Value>& info)
 {
     // FIXME: Consider passing StringImpl directly.
     AtomicString name = toCoreAtomicString(property);
@@ skipping 49 matching lines @@
 void V8WindowShell::updateSecurityOrigin(SecurityOrigin* origin)
 {
     ASSERT(m_world->isMainWorld());
     if (!m_perContextData)
         return;
     v8::HandleScope handleScope(m_isolate);
     setSecurityToken(origin);
 }
 
 } // WebCore