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

cc/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 "cc/scrollbar_layer.h"
 
 #include "base/basictypes.h"
 #include "base/debug/trace_event.h"
 #include "cc/caching_bitmap_content_layer_updater.h"
 #include "cc/layer_painter.h"
@@ skipping 46 matching lines @@
 
     m_scrollLayerId = id;
     setNeedsFullTreeSync();
 }
 
 WebKit::WebScrollbar::Orientation ScrollbarLayer::orientation() const
 {
     return m_scrollbar->orientation();
 }
 
+bool ScrollbarLayer::isOverlay() const
+{
+    return m_scrollbar->isOverlay();
+}
+
 int ScrollbarLayer::maxTextureSize() {
     DCHECK(layerTreeHost());
     return layerTreeHost()->rendererCapabilities().maxTextureSize;
 }
 
 float ScrollbarLayer::clampScaleToMaxTextureSize(float scale) {
     if (layerTreeHost()->settings().solidColorScrollbars)
         return scale;
 
     // If the scaled contentBounds() is bigger than the max texture size of the
@@ skipping 269 matching lines @@
     gfx::Rect thumbRect = m_geometry->thumbRect(m_scrollbar.get());
     m_thumbSize = thumbRect.size();
     gfx::Rect originThumbRect = scrollbarLayerRectToContentRect(gfx::Rect(thumbRect.size()));
     if (!originThumbRect.IsEmpty())
         updatePart(m_thumbUpdater.get(), m_thumb.get(), originThumbRect, queue, stats);
 
     m_dirtyRect = gfx::RectF();
 }
 
 }  // namespace cc