Remove unused includes from core/{editing,fileapi,history,html}

Source/core/html/shadow/HTMLContentElement.h

 /*
  * Copyright (C) 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 15 matching lines @@
  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef HTMLContentElement_h
 #define HTMLContentElement_h
 
 #include "core/css/CSSSelectorList.h"
 #include "core/dom/shadow/InsertionPoint.h"
-#include <wtf/Forward.h>
 
 namespace WebCore {
 
 class HTMLContentElement FINAL : public InsertionPoint {
 public:
     static const QualifiedName& contentTagName(Document*);
     static PassRefPtr<HTMLContentElement> create(const QualifiedName&, Document*);
     static PassRefPtr<HTMLContentElement> create(Document*);
 
     virtual ~HTMLContentElement();
@@ skipping 40 matching lines @@
 
 inline HTMLContentElement* toHTMLContentElement(Node* node)
 {
     ASSERT_WITH_SECURITY_IMPLICATION(!node || isHTMLContentElement(node));
     return static_cast<HTMLContentElement*>(node);
 }
 
 }
 
 #endif