Reland of place pinch scrollbars with regular scrollbars.

Source/core/frame/VisualViewport.h

 /*
  * Copyright (C) 2013 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 69 matching lines @@
     }
     GraphicsLayer* containerLayer()
     {
         return m_innerViewportContainerLayer.get();
     }
     GraphicsLayer* scrollLayer()
     {
         return m_innerViewportScrollLayer.get();
     }
 
+    void initializeScrollbars();
+
     // Sets the location of the visual viewport relative to the outer viewport. The
     // coordinates are in partial CSS pixels.
     void setLocation(const FloatPoint&);
     // FIXME: This should be called moveBy
     void move(const FloatPoint&);
     void move(const FloatSize&);
     FloatPoint location() const { return m_offset; }
 
     // Sets the size of the inner viewport when unscaled in CSS pixels.
     void setSize(const IntSize&);
@@ skipping 88 matching lines @@
     void setScrollOffset(const IntPoint&, ScrollType) override;
     void setScrollOffset(const DoublePoint&, ScrollType) override;
     GraphicsLayer* layerForContainer() const override;
     GraphicsLayer* layerForScrolling() const override;
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
 
 private:
     explicit VisualViewport(FrameHost&);
 
+    bool visualViewportSuppliesScrollbars() const;
+
     // GraphicsLayerClient implementation.
     void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& inClip) override;
     String debugName(const GraphicsLayer*) override;
 
     void setupScrollbar(WebScrollbar::Orientation);
     FloatPoint clampOffsetToBoundaries(const FloatPoint&);
 
     LocalFrame* mainFrame() const;
 
     FrameHost& frameHost() const
@@ skipping 16 matching lines @@
     // Offset of the visual viewport from the main frame's origin, in CSS pixels.
     FloatPoint m_offset;
     float m_scale;
     IntSize m_size;
     float m_topControlsAdjustment;
 };
 
 } // namespace blink
 
 #endif // VisualViewport_h