Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/pinch_zoom_scrollbar.h

Index: cc/pinch_zoom_scrollbar.h
diff --git a/cc/pinch_zoom_scrollbar.h b/cc/pinch_zoom_scrollbar.h
new file mode 100644
index 0000000000000000000000000000000000000000..7cf5a9de2da3cc72053d632fd5e135ffcb14be04
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar.h
@@ -0,0 +1,42 @@
+
+#ifndef CC_PINCH_ZOOM_SCROLLBAR_H_
+#define CC_PINCH_ZOOM_SCROLLBAR_H_
+
+#include "cc/cc_export.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebScrollbar.h"
+
+namespace cc {
+
+class LayerTreeHost;
+
+class CC_EXPORT PinchZoomScrollbar : public WebKit::WebScrollbar {
+ public:
+  PinchZoomScrollbar(WebKit::WebScrollbar::Orientation orientation, LayerTreeHost* owner);
+  virtual ~PinchZoomScrollbar() {}
+
+  virtual bool isOverlay() const OVERRIDE;
+  virtual int value() const OVERRIDE;
+  virtual WebKit::WebPoint location() const OVERRIDE;
+  virtual WebKit::WebSize size() const OVERRIDE;
+  virtual bool enabled() const OVERRIDE;
+  virtual int maximum() const OVERRIDE;
+  virtual int totalSize() const OVERRIDE;
+  virtual bool isScrollViewScrollbar() const OVERRIDE;
+  virtual bool isScrollableAreaActive() const OVERRIDE;
+  virtual void getTickmarks(WebKit::WebVector<WebKit::WebRect>&) const OVERRIDE {}
+  virtual WebKit::WebScrollbar::ScrollbarControlSize controlSize() const OVERRIDE;
+  virtual WebKit::WebScrollbar::ScrollbarPart pressedPart() const OVERRIDE;
+  virtual WebKit::WebScrollbar::ScrollbarPart hoveredPart() const OVERRIDE;
+  virtual WebKit::WebScrollbar::ScrollbarOverlayStyle scrollbarOverlayStyle() const OVERRIDE;
+  virtual bool isCustomScrollbar() const OVERRIDE;
+  virtual WebKit::WebScrollbar::Orientation orientation() const OVERRIDE;
+
+  static const int kTrackWidth = 10;
+
+ private:
+  WebKit::WebScrollbar::Orientation orientation_;
+  LayerTreeHost* owner_;
+};  // class PinchZoomScrollbar
+
+}  // namespace cc
+#endif // CC_PINCH_ZOOM_SCROLLBAR_H_