Add viewport scrollbar class to support overlay scrollbars for pinch zoom virtual viewport.

content/renderer/gpu/render_widget_compositor.cc

 // Copyright (c) 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.
 
 #include "content/renderer/gpu/render_widget_compositor.h"
 
 #include <limits>
 #include <string>
 
 #include "base/command_line.h"
@@ skipping 454 matching lines @@
 void RenderWidgetCompositor::didStopFlinging() {
   layer_tree_host_->DidStopFlinging();
 }
 
 void RenderWidgetCompositor::registerForAnimations(WebKit::WebLayer* layer) {
   cc::Layer* cc_layer = static_cast<webkit::WebLayerImpl*>(layer)->layer();
   cc_layer->layer_animation_controller()->SetAnimationRegistrar(
       layer_tree_host_->animation_registrar());
 }
 
+void RenderWidgetCompositor::registerPinchViewportLayers(
+    const WebKit::WebLayer* innerViewportClipLayer,
+    const WebKit::WebLayer* pageScaleLayerLayer,
+    const WebKit::WebLayer* innerViewportScrollLayer,
+    const WebKit::WebLayer* outerViewportScrollLayer,
+    const WebKit::WebLayer* innerViewportHorizontalScrollbarLayer,
+    const WebKit::WebLayer* innerViewportVerticalScrollbarLayer) {
+  layer_tree_host_->RegisterPinchViewportLayers(
+      static_cast<const webkit::WebLayerImpl*>(innerViewportClipLayer)
+          ->layer(),
+      static_cast<const webkit::WebLayerImpl*>(pageScaleLayerLayer)->layer(),
+      static_cast<const webkit::WebLayerImpl*>(innerViewportScrollLayer)
+          ->layer(),
+      static_cast<const webkit::WebLayerImpl*>(outerViewportScrollLayer)
+          ->layer(),
+      static_cast<const webkit::WebLayerImpl*>(
+          innerViewportHorizontalScrollbarLayer)->layer(),
+      static_cast<const webkit::WebLayerImpl*>(
+          innerViewportVerticalScrollbarLayer)->layer());
+}
+
+void RenderWidgetCompositor::clearPinchViewportLayers() {
+  layer_tree_host_->RegisterPinchViewportLayers(
+      scoped_refptr<cc::Layer>(),
+      scoped_refptr<cc::Layer>(),
+      scoped_refptr<cc::Layer>(),
+      scoped_refptr<cc::Layer>(),
+      scoped_refptr<cc::Layer>(),
+      scoped_refptr<cc::Layer>());
+}
+
 bool RenderWidgetCompositor::compositeAndReadback(
     void *pixels, const WebRect& rect_in_device_viewport) {
   return layer_tree_host_->CompositeAndReadback(pixels,
                                                 rect_in_device_viewport);
 }
 
 void RenderWidgetCompositor::finishAllRendering() {
   layer_tree_host_->FinishAllRendering();
 }
 
@@ skipping 83 matching lines @@
   return RenderThreadImpl::current()->OffscreenContextProviderForMainThread();
 }
 
 scoped_refptr<cc::ContextProvider>
 RenderWidgetCompositor::OffscreenContextProviderForCompositorThread() {
   return RenderThreadImpl::current()->
       OffscreenContextProviderForCompositorThread();
 }
 
 }  // namespace content