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

Source/core/loader/FrameLoader.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008 Alp Toker <alp@atoker.com>
  * Copyright (C) Research In Motion Limited 2009. All rights reserved.
  * Copyright (C) 2011 Kris Jordan <krisjordan@gmail.com>
  * Copyright (C) 2011 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ skipping 1382 matching lines @@
         ASSERT_NOT_REACHED();
         return false;
     }
 }
 
 bool FrameLoader::shouldTreatURLAsSrcdocDocument(const KURL& url) const
 {
     if (!equalIgnoringCase(url.string(), "about:srcdoc"))
         return false;
     HTMLFrameOwnerElement* ownerElement = m_frame->ownerElement();
-    if (!ownerElement)
-        return false;
-    if (!ownerElement->hasTagName(iframeTag))
+    if (!isHTMLIFrameElement(ownerElement))
         return false;
     return ownerElement->fastHasAttribute(srcdocAttr);
 }
 
 LocalFrame* FrameLoader::findFrameForNavigation(const AtomicString& name, Document* activeDocument)
 {
     ASSERT(activeDocument);
     LocalFrame* frame = m_frame->tree().find(name);
     if (!activeDocument->canNavigate(frame))
         return 0;
@@ skipping 44 matching lines @@
 {
     SandboxFlags flags = m_forcedSandboxFlags;
     if (LocalFrame* parentFrame = m_frame->tree().parent())
         flags |= parentFrame->document()->sandboxFlags();
     if (HTMLFrameOwnerElement* ownerElement = m_frame->ownerElement())
         flags |= ownerElement->sandboxFlags();
     return flags;
 }
 
 } // namespace WebCore