Introduce toHTMLIFrameElement

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 4727 matching lines @@
 void Document::resetLastHandledUserGestureTimestamp()
 {
     m_lastHandledUserGestureTimestamp = currentTime();
 }
 
 HTMLIFrameElement* Document::seamlessParentIFrame() const
 {
     if (!shouldDisplaySeamlesslyWithParent())
         return 0;
 
-    HTMLFrameOwnerElement* ownerElement = this->ownerElement();
-    ASSERT(ownerElement->hasTagName(iframeTag));
-    return static_cast<HTMLIFrameElement*>(ownerElement);
+    return toHTMLIFrameElement(this->ownerElement());
 }
 
 bool Document::shouldDisplaySeamlesslyWithParent() const
 {
     if (!RuntimeEnabledFeatures::seamlessIFramesEnabled())
         return false;
     HTMLFrameOwnerElement* ownerElement = this->ownerElement();
     if (!ownerElement)
         return false;
     return m_mayDisplaySeamlesslyWithParent && ownerElement->hasTagName(iframeTag) && ownerElement->fastHasAttribute(seamlessAttr);
@@ skipping 392 matching lines @@
 {
     return DocumentLifecycleNotifier::create(this);
 }
 
 DocumentLifecycleNotifier* Document::lifecycleNotifier()
 {
     return static_cast<DocumentLifecycleNotifier*>(ScriptExecutionContext::lifecycleNotifier());
 }
 
 } // namespace WebCore