Support high DPI scrollbar on top level web frame.

cc/CCLayerImpl.cpp

 // Copyright 2011 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 "config.h"
 
 #if USE(ACCELERATED_COMPOSITING)
 
 #include "CCLayerImpl.h"
 
@@ skipping 191 matching lines @@
     }
 
     if (!scrollable()) {
         TRACE_EVENT0("cc", "CCLayerImpl::tryScroll: Ignored not scrollable");
         return CCInputHandlerClient::ScrollIgnored;
     }
 
     return CCInputHandlerClient::ScrollStarted;
 }
 
+IntRect CCLayerImpl::layerRectToContentRect(const WebKit::WebRect& layerRect)
+{
+    float widthScale = static_cast<float>(contentBounds().width()) / bounds().width();
+    float heightScale = static_cast<float>(contentBounds().height()) / bounds().height();
+    FloatRect contentRect(layerRect.x, layerRect.y, layerRect.width, layerRect.height);
+    contentRect.scale(widthScale, heightScale);
+    return enclosingIntRect(contentRect);
+}
+
 std::string CCLayerImpl::indentString(int indent)
 {
     std::string str;
     for (int i = 0; i != indent; ++i)
         str.append("  ");
     return str;
 }
 
 void CCLayerImpl::dumpLayerProperties(std::string* str, int indent) const
 {
@@ skipping 422 matching lines @@
     if (!m_scrollbarAnimationController)
         m_scrollbarAnimationController = CCScrollbarAnimationController::create(this);
     m_scrollbarAnimationController->setVerticalScrollbarLayer(scrollbarLayer);
     m_scrollbarAnimationController->updateScrollOffset(this);
 }
 
 }
 
 
 #endif // USE(ACCELERATED_COMPOSITING)