Implement one-page-at-a-time mousewheel scrolling in the impl thread.

webkit/compositor_bindings/web_layer_impl.cc

 // 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 "webkit/compositor_bindings/web_layer_impl.h"
 
 #include "base/string_util.h"
 #include "cc/animation.h"
 #include "cc/layer.h"
 #include "cc/region.h"
@@ skipping 322 matching lines @@
 void WebLayerImpl::setMaxScrollPosition(WebSize maxScrollPosition)
 {
     m_layer->setMaxScrollOffset(maxScrollPosition);
 }
 
 WebSize WebLayerImpl::maxScrollPosition() const
 {
     return m_layer->maxScrollOffset();
 }
 
+void WebLayerImpl::setVisibleScrollArea(WebSize scrollArea)
+{
+    m_layer->setVisibleScrollArea(scrollArea);
+}
+
+WebSize WebLayerImpl::visibleScrollArea() const
+{
+    return m_layer->visibleScrollArea();
+}
+
 void WebLayerImpl::setScrollable(bool scrollable)
 {
     m_layer->setScrollable(scrollable);
 }
 
 bool WebLayerImpl::scrollable() const
 {
     return m_layer->scrollable();
 }
 
@@ skipping 88 matching lines @@
 {
     m_layer->setLayerScrollClient(scrollClient);
 }
 
 Layer* WebLayerImpl::layer() const
 {
     return m_layer.get();
 }
 
 } // namespace WebKit