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

content/common/gpu/image_transport_surface.cc

Index: content/common/gpu/image_transport_surface.cc
diff --git a/content/common/gpu/image_transport_surface.cc b/content/common/gpu/image_transport_surface.cc
index e1fadf609f1e54d800bee89b96fe1f0ebacfd490..9fa8e112cae5af8a010e101ea18fef30fbbf41e9 100644
--- a/content/common/gpu/image_transport_surface.cc
+++ b/content/common/gpu/image_transport_surface.cc
@@ -96,6 +96,8 @@ bool ImageTransportHelper::OnMessageReceived(const IPC::Message& message) {
                         OnPostSubBufferACK)
     IPC_MESSAGE_HANDLER(AcceleratedSurfaceMsg_NewACK,
                         OnNewSurfaceACK)
+    IPC_MESSAGE_HANDLER(AcceleratedSurfaceMsg_DiscardSurface,
+                        OnDiscardSurface)
     IPC_MESSAGE_HANDLER(AcceleratedSurfaceMsg_ResizeViewACK, OnResizeViewACK);
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
@@ -139,6 +141,13 @@ void ImageTransportHelper::SendAcceleratedSurfaceRelease(
   manager_->Send(new GpuHostMsg_AcceleratedSurfaceRelease(params));
 }
 
+void ImageTransportHelper::SendAcceleratedSurfaceSuggestDiscard(
+    GpuHostMsg_AcceleratedSurfaceSuggestDiscard_Params params) {
+  params.surface_id = stub_->surface_id();
+  params.route_id = route_id_;
+  manager_->Send(new GpuHostMsg_AcceleratedSurfaceSuggestDiscard(params));
+}
+
 void ImageTransportHelper::SendResizeView(const gfx::Size& size) {
   manager_->Send(new GpuHostMsg_ResizeView(stub_->surface_id(),
                                            route_id_,
@@ -201,6 +210,11 @@ void ImageTransportHelper::OnNewSurfaceACK(
   surface_->OnNewSurfaceACK(surface_handle, shm_handle);
 }
 
+void ImageTransportHelper::OnDiscardSurface(
+    uint64 surface_id) {
+  surface_->OnDiscardSurface(surface_id);
+}
+
 void ImageTransportHelper::OnBuffersSwappedACK() {
   surface_->OnBuffersSwappedACK();
 }
@@ -305,6 +319,10 @@ void PassThroughImageTransportSurface::OnNewSurfaceACK(
     TransportDIB::Handle shm_handle) {
 }
 
+void PassThroughImageTransportSurface::OnDiscardSurface(
+    uint64 surface_id) {
+}
+
 void PassThroughImageTransportSurface::OnBuffersSwappedACK() {
   DCHECK(transport_);
   helper_->SetScheduled(true);