Reland of place pinch scrollbars with regular scrollbars.

Source/core/frame/FrameView.h

 /*
    Copyright (C) 1997 Martin Jones (mjones@kde.org)
              (C) 1998 Waldo Bastian (bastian@kde.org)
              (C) 1998, 1999 Torben Weis (weis@kde.org)
              (C) 1999 Lars Knoll (knoll@kde.org)
              (C) 1999 Antti Koivisto (koivisto@kde.org)
    Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
 
    This library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Library General Public
@@ skipping 327 matching lines @@
 
     IntPoint maximumScrollPosition() const override;
 
     // ScrollableArea interface
     void invalidateScrollbarRect(Scrollbar*, const IntRect&) override;
     void getTickmarks(Vector<IntRect>&) const override;
     void scrollTo(const DoublePoint&);
     IntRect scrollableAreaBoundingBox() const override;
     bool scrollAnimatorEnabled() const override;
     bool usesCompositedScrolling() const override;
+    GraphicsLayer* layerForScrollbarContainer() const override;
     GraphicsLayer* layerForScrolling() const override;
     GraphicsLayer* layerForHorizontalScrollbar() const override;
     GraphicsLayer* layerForVerticalScrollbar() const override;
     GraphicsLayer* layerForScrollCorner() const override;
     int scrollSize(ScrollbarOrientation) const override;
     bool isScrollCornerVisible() const override;
     bool userInputScrollable(ScrollbarOrientation) const override;
     bool shouldPlaceVerticalScrollbarOnLeft() const override;
     virtual LayoutRect scrollIntoView(
         const LayoutRect& rectInContent,
@@ skipping 501 matching lines @@
     static const unsigned visualPixelThreshold = 32 * 32;
     if (m_visuallyNonEmptyPixelCount > visualPixelThreshold)
         setIsVisuallyNonEmpty();
 }
 
 DEFINE_TYPE_CASTS(FrameView, Widget, widget, widget->isFrameView(), widget.isFrameView());
 
 } // namespace blink
 
 #endif // FrameView_h