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

cc/pinch_zoom_scrollbar.h

+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#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;

[jamesr, 2013/02/26 20:48:46]

document what interface this is overriding.

Don't use OVERRIDE when the declaration of the interface is in a different repo
(i.e. WebKit) from the override

[wjmaclean, 2013/03/01 15:30:32]

Done.

+  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;

[jamesr, 2013/02/26 20:48:46]

It's not good practice to put a constant's definition in a header like this
since many translation units will include this header. To declare a static
constant, put the declaration in the header but put the definition (and value)
in the .cc to define storage

[wjmaclean, 2013/03/01 15:30:32]

Done.

+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PinchZoomScrollbar);
+
+  WebKit::WebScrollbar::Orientation orientation_;
+  LayerTreeHost* owner_;
+};  // class PinchZoomScrollbar
+
+}  // namespace cc
+#endif // CC_PINCH_ZOOM_SCROLLBAR_H_