blink: Cleanup class/struct forward declarations

third_party/WebKit/Source/platform/scroll/ScrollbarThemeMac.h

 /*
  * Copyright (C) 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #ifndef ScrollbarThemeMac_h
 #define ScrollbarThemeMac_h
 
 #include "platform/mac/NSScrollerImpDetails.h"
 #include "platform/scroll/ScrollbarTheme.h"
 
 typedef id ScrollbarPainter;
 
-class SkCanvas;
-
 namespace blink {
 
 class Pattern;
 
 class PLATFORM_EXPORT ScrollbarThemeMac : public ScrollbarTheme {
  public:
   ~ScrollbarThemeMac() override;
 
   void registerScrollbar(ScrollbarThemeClient&) override;
   void unregisterScrollbar(ScrollbarThemeClient&) override;
@@ skipping 64 matching lines @@
 
   int minimumThumbLength(const ScrollbarThemeClient&) override;
 
   int tickmarkBorderWidth() override { return 1; }
 
   RefPtr<Pattern> m_overhangPattern;
 };
 }
 
 #endif  // ScrollbarThemeMac_h