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

cc/pinch_zoom_scrollbar_painter.h

Index: cc/pinch_zoom_scrollbar_painter.h
diff --git a/cc/pinch_zoom_scrollbar_painter.h b/cc/pinch_zoom_scrollbar_painter.h
new file mode 100644
index 0000000000000000000000000000000000000000..ae0fc382efaa9b718ac3e9db19e4502c5328d960
--- /dev/null
+++ b/cc/pinch_zoom_scrollbar_painter.h
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+// 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_PAINTER_H_
+#define CC_PINCH_ZOOM_SCROLLBAR_PAINTER_H_
+
+#include "base/compiler_specific.h"
+#include "cc/scrollbar_theme_painter.h"
+
+namespace cc {
+
+class PinchZoomScrollbarPainter : public ScrollbarThemePainter {
+ public:
+  PinchZoomScrollbarPainter() {}
+  virtual ~PinchZoomScrollbarPainter();
+
+  virtual void PaintScrollbarBackground(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintTrackBackground(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintBackTrackPart(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintForwardTrackPart(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintBackButtonStart(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintBackButtonEnd(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintForwardButtonStart(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintForwardButtonEnd(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintTickmarks(
+    SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+  virtual void PaintThumb(SkCanvas* canvas, const gfx::Rect& rect) OVERRIDE;
+};
+
+}  // namespace cc
+
+#endif  // CC_PINCH_ZOOM_SCROLLBAR_PAINTER_H_