Remove unused includes from core/html .cpp files

Source/core/html/HTMLCollection.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 10 matching lines @@
  */
 
 #include "config.h"
 #include "core/html/HTMLCollection.h"
 
 #include "HTMLNames.h"
 #include "core/dom/ClassNodeList.h"
 #include "core/dom/NodeList.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/NodeTraversal.h"
-#include "core/html/HTMLDocument.h"
 #include "core/html/HTMLElement.h"
 #include "core/html/HTMLObjectElement.h"
 #include "core/html/HTMLOptionElement.h"
 
 #include <utility>
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
@@ skipping 644 matching lines @@
 
 void HTMLCollection::append(NodeCacheMap& map, const AtomicString& key, Element* element)
 {
     OwnPtr<Vector<Element*> >& vector = map.add(key.impl(), nullptr).iterator->value;
     if (!vector)
         vector = adoptPtr(new Vector<Element*>);
     vector->append(element);
 }
 
 } // namespace WebCore