Hide scrollbars when their dimensions are not scrollable.

Source/core/frame/PinchViewport.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 100 matching lines @@
 
     // Scroll the main frame and pinch viewport so that the given rect in the
     // top-level document is centered in the viewport. This method will avoid
     // scrolling the pinch viewport unless necessary.
     void scrollIntoView(const FloatRect&);
 
     // Clamp the given point, in document coordinates, to the maximum/minimum
     // scroll extents of the viewport within the document.
     IntPoint clampDocumentOffsetAtScale(const IntPoint& offset, float scale);
 
+    void adjustScrollbarExistence();
+
+    // Used in tests
+    virtual GraphicsLayer* layerForHorizontalScrollbar() const override;
+    virtual GraphicsLayer* layerForVerticalScrollbar() const override;
+
 private:
     // ScrollableArea implementation
     virtual bool isActive() const override { return false; }
     virtual int scrollSize(ScrollbarOrientation) const override;
     virtual bool isScrollCornerVisible() const override { return false; }
     virtual IntRect scrollCornerRect() const override { return IntRect(); }
     virtual IntPoint scrollPosition() const override { return flooredIntPoint(m_offset); }
     virtual IntPoint minimumScrollPosition() const override;
     virtual IntPoint maximumScrollPosition() const override;
     virtual int visibleHeight() const override { return visibleRect().height(); };
     virtual int visibleWidth() const override { return visibleRect().width(); };
     virtual IntSize contentsSize() const override;
     virtual bool scrollbarsCanBeActive() const override { return false; }
     virtual IntRect scrollableAreaBoundingBox() const override;
     virtual bool userInputScrollable(ScrollbarOrientation) const override { return true; }
     virtual bool shouldPlaceVerticalScrollbarOnLeft() const override { return false; }
     virtual void invalidateScrollbarRect(Scrollbar*, const IntRect&) override;
     virtual void invalidateScrollCornerRect(const IntRect&) override { }
     virtual void setScrollOffset(const IntPoint&) override;
     virtual GraphicsLayer* layerForContainer() const override;
     virtual GraphicsLayer* layerForScrolling() const override;
-    virtual GraphicsLayer* layerForHorizontalScrollbar() const override;
-    virtual GraphicsLayer* layerForVerticalScrollbar() const override;
 
     // GraphicsLayerClient implementation.
     virtual void notifyAnimationStarted(const GraphicsLayer*, double monotonicTime) override;
     virtual void paintContents(const GraphicsLayer*, GraphicsContext&, GraphicsLayerPaintingPhase, const IntRect& inClip) override;
     virtual String debugName(const GraphicsLayer*) override;
 
     void setupScrollbar(blink::WebScrollbar::Orientation);
     FloatPoint clampOffsetToBoundaries(const FloatPoint&);
     void clampToBoundaries();
 
     LocalFrame* mainFrame() const;
 
     FrameHost& m_frameHost;
     OwnPtr<GraphicsLayer> m_rootTransformLayer;
     OwnPtr<GraphicsLayer> m_innerViewportContainerLayer;
     OwnPtr<GraphicsLayer> m_pageScaleLayer;
     OwnPtr<GraphicsLayer> m_innerViewportScrollLayer;
     OwnPtr<GraphicsLayer> m_overlayScrollbarHorizontal;
     OwnPtr<GraphicsLayer> m_overlayScrollbarVertical;
     OwnPtr<blink::WebScrollbarLayer> m_webOverlayScrollbarHorizontal;
     OwnPtr<blink::WebScrollbarLayer> m_webOverlayScrollbarVertical;
 
     // Offset of the pinch viewport from the main frame's origin, in CSS pixels.
     FloatPoint m_offset;
     float m_scale;
     IntSize m_size;
+
+    bool m_hasHorizontalScrollbar;
+    bool m_hasVerticalScrollbar;
 };
 
 } // namespace blink
 
 #endif // PinchViewport_h