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

cc/pinch_zoom_scrollbar_layer.cc

+// Copyright 2012 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.
+
+#include "pinch_zoom_scrollbar_layer.h"
+
+#include "scrollbar_layer_impl.h"
+
+namespace cc {
+
+scoped_refptr<PinchZoomScrollbarLayer> PinchZoomScrollbarLayer::create()
+{
+    return make_scoped_refptr(new PinchZoomScrollbarLayer());
+}
+
+PinchZoomScrollbarLayer::PinchZoomScrollbarLayer()
+{
+}
+
+scoped_ptr<LayerImpl> PinchZoomScrollbarLayer::createLayerImpl(LayerTreeImpl* treeImpl)
+{
+    return ScrollbarLayerImpl::create(treeImpl, id()).PassAs<LayerImpl>();
+}
+
+bool PinchZoomScrollbarLayer::drawsContent() const
+{
+    return true;
+}
+
+} // namespace cc