Clean up forward declarations in Source/platform

Source/platform/exported/WebScrollbarThemeClientImpl.h

 /*
  * Copyright (C) 2012 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:
  *
  * 1.  Redistributions of source code must retain the above copyright
  *     notice, this list of conditions and the following disclaimer.
  * 2.  Redistributions in binary form must reproduce the above copyright
@@ skipping 14 matching lines @@
 
 #ifndef WebScrollbarThemeClientImpl_h
 #define WebScrollbarThemeClientImpl_h
 
 #include "platform/PlatformExport.h"
 #include "platform/scroll/ScrollbarThemeClient.h"
 #include "public/platform/WebScrollbar.h"
 #include "wtf/Noncopyable.h"
 
 namespace blink {
-class ScrollView;
 
 // Adapts a WebScrollbar to the ScrollbarThemeClient interface
 class PLATFORM_EXPORT WebScrollbarThemeClientImpl : public ScrollbarThemeClient {
     WTF_MAKE_NONCOPYABLE(WebScrollbarThemeClientImpl);
 public:
     // Caller must retain ownership of this pointer and ensure that its lifetime
     // exceeds this instance.
     WebScrollbarThemeClientImpl(WebScrollbar*);
     virtual ~WebScrollbarThemeClientImpl();
 
@@ skipping 33 matching lines @@
     virtual bool isAlphaLocked() const OVERRIDE;
     virtual void setIsAlphaLocked(bool) OVERRIDE;
 
 private:
     WebScrollbar* m_scrollbar;
 };
 
 } // namespace blink
 
 #endif // WebScrollbarThemeClientImpl_h