Remove redundant forward declaration and header inclusion.

Source/core/html/HTMLStyleElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2010 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 11 matching lines @@
 
 #ifndef HTMLStyleElement_h
 #define HTMLStyleElement_h
 
 #include "core/dom/StyleElement.h"
 #include "core/html/HTMLElement.h"
 
 namespace WebCore {
 
 class HTMLStyleElement;
-class StyleSheet;
 
 template<typename T> class EventSender;
 typedef EventSender<HTMLStyleElement> StyleEventSender;
 
 class HTMLStyleElement FINAL : public HTMLElement, private StyleElement {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(HTMLStyleElement);
 public:
     static PassRefPtrWillBeRawPtr<HTMLStyleElement> create(Document&, bool createdByParser);
     virtual ~HTMLStyleElement();
 
@@ skipping 28 matching lines @@
     virtual const AtomicString& media() const OVERRIDE;
     virtual const AtomicString& type() const OVERRIDE;
 
     bool m_firedLoad;
     bool m_loadedSheet;
 };
 
 } //namespace
 
 #endif