Move ScrollBehavior to ScrollTypes.h, so that ComputedStyle.h doesn't need to include ScrollableAre…

third_party/WebKit/Source/core/layout/LayoutScrollbarPart.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 14 matching lines @@
 
 #ifndef LayoutScrollbarPart_h
 #define LayoutScrollbarPart_h
 
 #include "core/layout/LayoutBlock.h"
 #include "platform/scroll/ScrollTypes.h"
 
 namespace blink {
 
 class LayoutScrollbar;
+class ScrollableArea;
 
 class LayoutScrollbarPart final : public LayoutBlock {
 public:
     static LayoutScrollbarPart* createAnonymous(Document*, ScrollableArea*,
         LayoutScrollbar* = nullptr, ScrollbarPart = NoPart);
     ~LayoutScrollbarPart() override;
 
     const char* name() const override { return "LayoutScrollbarPart"; }
 
     PaintLayerType layerTypeRequired() const override { return NoPaintLayer; }
@@ skipping 71 matching lines @@
     UntracedMember<ScrollableArea> m_scrollableArea;
     UntracedMember<LayoutScrollbar> m_scrollbar;
     ScrollbarPart m_part;
 };
 
 DEFINE_LAYOUT_OBJECT_TYPE_CASTS(LayoutScrollbarPart, isLayoutScrollbarPart());
 
 } // namespace blink
 
 #endif // LayoutScrollbarPart_h