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

cc/pinch_zoom_scrollbar_geometry.h

Index: cc/pinch_zoom_scrollbar_geometry.h
diff --git a/cc/pinch_zoom_scrollbar_geometry.h b/cc/pinch_zoom_scrollbar_geometry.h
new file mode 100644
index 0000000000000000000000000000000000000000..0e81982fc8c2e694dba733cc391ec980c4a46c99
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+++ b/cc/pinch_zoom_scrollbar_geometry.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_GEOMETRY_H_
+#define CC_PINCH_ZOOM_SCROLLBAR_GEOMETRY_H_
+
+#include "cc/cc_export.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebScrollbarThemeGeometry.h"
+
+using WebKit::WebScrollbar;
+using WebKit::WebRect;
+using WebKit::WebScrollbarThemeGeometry;
+
+namespace cc {
+
+class CC_EXPORT PinchZoomScrollbarGeometry : public WebScrollbarThemeGeometry {
+ public:
+  virtual ~PinchZoomScrollbarGeometry() {}
+
+  static const int kTrackWidth;
+
+  // Implement WebScrollbarThemeGeometry interface.
+  virtual WebScrollbarThemeGeometry* clone() const;
+  virtual int thumbPosition(WebScrollbar* scrollbar);
+  virtual int thumbLength(WebScrollbar* scrollbar);
+  virtual int trackPosition(WebScrollbar* scrollbar);
+  virtual int trackLength(WebScrollbar* scrollbar);
+  virtual bool hasButtons(WebScrollbar* scrollbar);
+  virtual bool hasThumb(WebScrollbar* scrollbar);
+  virtual WebRect trackRect(WebScrollbar* scrollbar);
+  virtual WebRect thumbRect(WebScrollbar* scrollbar);
+  virtual int minimumThumbLength(WebScrollbar* scrollbar);
+  virtual int scrollbarThickness(WebScrollbar* scrollbar);
+  virtual WebRect backButtonStartRect(WebScrollbar* scrollbar);
+  virtual WebRect backButtonEndRect(WebScrollbar* scrollbar);
+  virtual WebRect forwardButtonStartRect(WebScrollbar* scrollbar);
+  virtual WebRect forwardButtonEndRect(WebScrollbar* scrollbar);
+
+  virtual WebRect constrainTrackRectToTrackPieces(WebScrollbar* scrollbar,
+    const WebRect& trackRect);
+
+  virtual void splitTrack(
+    WebScrollbar* scrollbar, const WebRect& track, WebRect& start_track,
+    WebRect& thumb, WebRect& end_track);
+
+};
+
+} // namespace WebKit
+#endif  // CC_PINCH_ZOOM_SCROLLBAR_GEOMETRY_H_