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

content/common/gpu/gpu_messages.h

Index: content/common/gpu/gpu_messages.h
diff --git a/content/common/gpu/gpu_messages.h b/content/common/gpu/gpu_messages.h
index d921b3bcdd34a54b5f84017c1bd6233f13bf99c1..48623495b69ad1e9f850254a55d69e281786cf5e 100644
--- a/content/common/gpu/gpu_messages.h
+++ b/content/common/gpu/gpu_messages.h
@@ -84,6 +84,12 @@ IPC_STRUCT_BEGIN(GpuHostMsg_AcceleratedSurfaceRelease_Params)
 #endif
 IPC_STRUCT_END()
 
+IPC_STRUCT_BEGIN(GpuHostMsg_AcceleratedSurfaceSuggestDiscard_Params)
+  IPC_STRUCT_MEMBER(int32, surface_id)
+  IPC_STRUCT_MEMBER(uint64, identifier)
+  IPC_STRUCT_MEMBER(int32, route_id)
+IPC_STRUCT_END()
+
 IPC_STRUCT_BEGIN(GPUCommandBufferConsoleMessage)
   IPC_STRUCT_MEMBER(int32, id)
   IPC_STRUCT_MEMBER(std::string, message)
@@ -192,6 +198,10 @@ IPC_MESSAGE_ROUTED2(AcceleratedSurfaceMsg_NewACK,
                     uint64 /* surface_handle */,
                     TransportDIB::Handle /* shared memory buffer */)
 
+// Tells the GPU process that it's safe to release the surface.
+IPC_MESSAGE_ROUTED1(AcceleratedSurfaceMsg_DiscardSurface,
+                    uint64 /* surface_id */)
+
 // Tells the GPU process that the browser process handled the swap
 // buffers request.
 IPC_MESSAGE_ROUTED0(AcceleratedSurfaceMsg_BuffersSwappedACK)
@@ -287,6 +297,11 @@ IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceRelease,
 IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceSuspend,
                      int32 /* surface_id */)
 
+// Tells the browser to release resources for the given surface until the next
+// time swap buffers or post sub buffer is sent.
+IPC_MESSAGE_CONTROL1(GpuHostMsg_AcceleratedSurfaceSuggestDiscard,
+                     GpuHostMsg_AcceleratedSurfaceSuggestDiscard_Params)
+
 //------------------------------------------------------------------------------
 // GPU Channel Messages
 // These are messages from a renderer process to the GPU process.