Drop frontbuffers with ui-use-gpu-process, synchronized with browser, decoupled from backbuffer dro…

content/browser/renderer_host/render_widget_host_impl.cc

Index: content/browser/renderer_host/render_widget_host_impl.cc
diff --git a/content/browser/renderer_host/render_widget_host_impl.cc b/content/browser/renderer_host/render_widget_host_impl.cc
index 781eccbdb97758f02200565e5304122c63d33843..d3768904fd0acf4f3a7ce7e1e988ae6222939c30 100644
--- a/content/browser/renderer_host/render_widget_host_impl.cc
+++ b/content/browser/renderer_host/render_widget_host_impl.cc
@@ -1805,6 +1805,17 @@ void RenderWidgetHostImpl::AcknowledgePostSubBuffer(int32 route_id,
     ui_shim->Send(new AcceleratedSurfaceMsg_PostSubBufferACK(route_id));
 }
 
+#if defined(USE_AURA)
+// static
+void RenderWidgetHostImpl::SendSurfaceDiscard(
+    uint64 surface_id, int32 route_id, int gpu_host_id) {
+  GpuProcessHostUIShim* ui_shim = GpuProcessHostUIShim::FromID(gpu_host_id);
+  if (ui_shim)
+    ui_shim->Send(new AcceleratedSurfaceMsg_DiscardSurface(route_id,
+                                                           surface_id));
+}
+#endif
+
 void RenderWidgetHostImpl::DelayedAutoResized() {
   gfx::Size new_size = new_auto_size_;
   // Clear the new_auto_size_ since the empty value is used as a flag to