Move ScrollbarManager from core to platform and use as Scrollbar parent

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

 /*
  * Copyright (C) 2008, 2011 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 14 matching lines @@
 
 #ifndef ScrollableArea_h
 #define ScrollableArea_h
 
 #include "platform/PlatformExport.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/FloatQuad.h"
 #include "platform/geometry/LayoutRect.h"
 #include "platform/graphics/Color.h"
 #include "platform/heap/Handle.h"
-#include "platform/scroll/ScrollAnimatorBase.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "platform/scroll/Scrollbar.h"
 #include "platform/wtf/MathExtras.h"
 #include "platform/wtf/Noncopyable.h"
 #include "platform/wtf/Vector.h"
 #include "public/platform/WebLayerScrollClient.h"
 
 namespace blink {
 
 class CompositorAnimationHost;
@@ skipping 404 matching lines @@
   // vertical-lr / ltr            NO                      NO
   // vertical-lr / rtl            NO                      YES
   // vertical-rl / ltr            YES                     NO
   // vertical-rl / rtl            YES                     YES
   IntPoint scroll_origin_;
 };
 
 }  // namespace blink
 
 #endif  // ScrollableArea_h