Move ScrollbarManager from core to platform and use as Scrollbar parent

third_party/WebKit/Source/core/frame/FrameView.h

Index: third_party/WebKit/Source/core/frame/FrameView.h
diff --git a/third_party/WebKit/Source/core/frame/FrameView.h b/third_party/WebKit/Source/core/frame/FrameView.h
index 061869d708f1de0111c96ba48d060c4c8b146b51..eb6b8665948765e2845f4c387f27a2ae2277f1b4 100644
--- a/third_party/WebKit/Source/core/frame/FrameView.h
+++ b/third_party/WebKit/Source/core/frame/FrameView.h
@@ -39,7 +39,6 @@
 #include "core/paint/ObjectPaintProperties.h"
 #include "core/paint/PaintInvalidationCapableScrollableArea.h"
 #include "core/paint/PaintPhase.h"
-#include "core/paint/ScrollbarManager.h"
 #include "core/plugins/PluginView.h"
 #include "platform/FrameViewBase.h"
 #include "platform/RuntimeEnabledFeatures.h"
@@ -52,6 +51,7 @@
 #include "platform/graphics/GraphicsLayerClient.h"
 #include "platform/scroll/ScrollTypes.h"
 #include "platform/scroll/Scrollbar.h"
+#include "platform/scroll/ScrollbarManager.h"
 #include "platform/wtf/Allocator.h"
 #include "platform/wtf/AutoReset.h"
 #include "platform/wtf/Forward.h"
@@ -103,6 +103,7 @@ typedef unsigned long long DOMTimeStamp;
 
 class CORE_EXPORT FrameView final
     : public FrameViewBase,
+      public ScrollbarManager,
       public FrameOrPlugin,
       public PaintInvalidationCapableScrollableArea {
   USING_GARBAGE_COLLECTED_MIXIN(FrameView);
@@ -485,15 +486,6 @@ class CORE_EXPORT FrameView final
   void AddScrollbar(Scrollbar*);
   const ScrollbarsSet* Scrollbars() const { return &scrollbars_; }
 
-  // If the scroll view does not use a native widget, then it will have
-  // cross-platform Scrollbars. These functions can be used to obtain those
-  // scrollbars.
-  Scrollbar* HorizontalScrollbar() const override {
-    return scrollbar_manager_.HorizontalScrollbar();
-  }
-  Scrollbar* VerticalScrollbar() const override {
-    return scrollbar_manager_.VerticalScrollbar();
-  }
   LayoutScrollbarPart* ScrollCorner() const override { return scroll_corner_; }
 
   void PositionScrollbarLayers();
@@ -542,6 +534,10 @@ class CORE_EXPORT FrameView final
            VerticalScrollbarMode() != kScrollbarAlwaysOff;
   }
 
+  void SetHasHorizontalScrollbar(bool) override;
+  void SetHasVerticalScrollbar(bool) override;
+  void DestroyScrollbar(ScrollbarOrientation) override;
+
   // The visible content rect has a location that is the scrolled offset of
   // the document. The width and height are the layout viewport width and
   // height. By default the scrollbars themselves are excluded from this
@@ -875,25 +871,6 @@ class CORE_EXPORT FrameView final
   void InvalidateTreeIfNeeded(const PaintInvalidationState&);
 
  private:
-  explicit FrameView(LocalFrame&);
-  class ScrollbarManager : public blink::ScrollbarManager {
-    DISALLOW_NEW();
-
-    // Helper class to manage the life cycle of Scrollbar objects.
-   public:
-    ScrollbarManager(FrameView& scroller) : blink::ScrollbarManager(scroller) {}
-
-    void SetHasHorizontalScrollbar(bool has_scrollbar) override;
-    void SetHasVerticalScrollbar(bool has_scrollbar) override;
-
-    // TODO(ymalik): This should be hidden and all calls should go through
-    // setHas*Scrollbar functions above.
-    Scrollbar* CreateScrollbar(ScrollbarOrientation) override;
-
-   protected:
-    void DestroyScrollbar(ScrollbarOrientation) override;
-  };
-
   void UpdateScrollOffset(const ScrollOffset&, ScrollType) override;
 
   void UpdateScrollbarEnabledState();
@@ -1183,9 +1160,6 @@ class CORE_EXPORT FrameView final
       HeapLinkedHashSet<WeakMember<ScrollableArea>>;
   AnchoringAdjustmentQueue anchoring_adjustment_queue_;
 
-  // ScrollbarManager holds the Scrollbar instances.
-  ScrollbarManager scrollbar_manager_;
-
   bool needs_scrollbars_update_;
   bool suppress_adjust_view_size_;
   bool allows_layout_invalidation_after_layout_clean_;