Expose locks for CopyFromCompositingSurface/CopyFromBackingStore API

content/browser/renderer_host/render_widget_host_view_base.cc

Index: content/browser/renderer_host/render_widget_host_view_base.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_base.cc b/content/browser/renderer_host/render_widget_host_view_base.cc
index d922c93ceb9ce9f2aba3ceb0e490bc900dfa1e1f..0fedf241324f7e04b6d1bae10097651c7d6bb5df 100644
--- a/content/browser/renderer_host/render_widget_host_view_base.cc
+++ b/content/browser/renderer_host/render_widget_host_view_base.cc
@@ -593,6 +593,10 @@ void RenderWidgetHostViewBase::DidReceiveRendererFrame() {
   ++renderer_frame_number_;
 }
 
+void RenderWidgetHostViewBase::LockSurfaceForCopy() {}
+
+void RenderWidgetHostViewBase::UnlockSurfaceForCopy() {}
+
 void RenderWidgetHostViewBase::FlushInput() {
   RenderWidgetHostImpl* impl = NULL;
   if (GetRenderWidgetHost())