Add viewport scrollbar class to support overlay scrollbars for pinch zoom virtual viewport.

cc/input/inner_viewport_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_INPUT_INNER_VIEWPORT_SCROLLBAR_H_
+#define CC_INPUT_INNER_VIEWPORT_SCROLLBAR_H_
+
+#include "base/memory/ref_counted.h"
+#include "cc/base/cc_export.h"
+#include "cc/input/scrollbar.h"
+#include "ui/gfx/point.h"
+#include "ui/gfx/rect.h"
+
+namespace cc {
+
+class Layer;
+
+class CC_EXPORT InnerViewportScrollbar : public Scrollbar {
+ public:
+  InnerViewportScrollbar(scoped_refptr<Layer> scroll_layer,
+                         scoped_refptr<Layer> clip_layer_,
+                         ScrollbarOrientation orientation,
+                         size_t thickness);
+  virtual ~InnerViewportScrollbar();
+
+  virtual ScrollbarOrientation Orientation() const OVERRIDE;
+  virtual gfx::Point Location() const OVERRIDE;
+  virtual bool IsOverlay() const OVERRIDE;
+  virtual bool HasThumb() const OVERRIDE;
+  virtual int ThumbThickness() const OVERRIDE;
+  virtual int ThumbLength() const OVERRIDE;
+  virtual gfx::Rect TrackRect() const OVERRIDE;
+  virtual void PaintPart(SkCanvas* canvas,
+                         ScrollbarPart part,
+                         gfx::Rect content_rect) OVERRIDE;
+
+ private:
+  scoped_refptr<Layer> scroll_layer_;
+  scoped_refptr<Layer> clip_layer_;
+  ScrollbarOrientation orientation_;
+  const size_t thickness_;
+};
+
+}  // namespace cc
+
+#endif  // CC_INPUT_INNER_VIEWPORT_SCROLLBAR_H_