Consistently use ElementTraversal API when looking for an Element

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 2305 matching lines @@
     setReadyState(Loading);
 
     return m_parser;
 }
 
 HTMLElement* Document::body() const
 {
     if (!documentElement())
         return 0;
 
-    for (Node* child = documentElement()->firstChild(); child; child = child->nextSibling()) {
+    for (Element* child = ElementTraversal::firstWithin(*documentElement()); child; child = ElementTraversal::nextSibling(*child)) {
         if (child->hasTagName(framesetTag) || child->hasTagName(bodyTag))
             return toHTMLElement(child);
     }
 
     return 0;
 }
 
 void Document::setBody(PassRefPtr<HTMLElement> prpNewBody, ExceptionState& exceptionState)
 {
     RefPtr<HTMLElement> newBody = prpNewBody;
@@ skipping 21 matching lines @@
     else
         documentElement()->appendChild(newBody.release(), exceptionState);
 }
 
 HTMLHeadElement* Document::head()
 {
     Node* de = documentElement();
     if (!de)
         return 0;
 
-    for (Node* node = de->firstChild(); node; node = node->nextSibling()) {
-        if (node->hasTagName(headTag))
-            return toHTMLHeadElement(node);
+    for (Element* child = ElementTraversal::firstWithin(*de); child; child = ElementTraversal::nextSibling(*child)) {
+        if (child->hasTagName(headTag))
+            return toHTMLHeadElement(child);
     }
     return 0;
 }
 
 Element* Document::viewportDefiningElement(RenderStyle* rootStyle) const
 {
     // If a BODY element sets non-visible overflow, it is to be propagated to the viewport, as long
     // as the following conditions are all met:
     // (1) The root element is HTML.
     // (2) It is the primary BODY element (we only assert for this, expecting callers to behave).
@@ skipping 3060 matching lines @@
 void Document::defaultEventHandler(Event* event)
 {
     if (frame() && frame()->remotePlatformLayer()) {
         frame()->chromeClient().forwardInputEvent(this, event);
         return;
     }
     Node::defaultEventHandler(event);
 }
 
 } // namespace WebCore