Implemented new fence syncs which replaces the old sync points.

content/common/gpu/gpu_messages.h

 // Copyright (c) 2012 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.
 
 // Multiply-included message file, hence no include guard here, but see below
 // for a much smaller-than-usual include guard section.
 
 #include <string>
 #include <vector>
 
@@ skipping 462 matching lines @@
                             GPUCreateCommandBufferConfig, /* init_params */
                             int32, /* route_id */
                             bool /* succeeded */)
 
 // The CommandBufferProxy sends this to the GpuCommandBufferStub in its
 // destructor, so that the stub deletes the actual CommandBufferService
 // object that it's hosting.
 IPC_SYNC_MESSAGE_CONTROL1_0(GpuChannelMsg_DestroyCommandBuffer,
                             int32 /* instance_id */)
 
+// Simple NOP message which can be used as fence to ensure all previous sent
+// messages have been received.
+IPC_SYNC_MESSAGE_CONTROL0_0(GpuChannelMsg_Nop)
+
 #if defined(OS_ANDROID)
 //------------------------------------------------------------------------------
 // Stream Texture Messages
 // Tells the GPU process create and send the java surface texture object to
 // the renderer process through the binder thread.
 IPC_MESSAGE_ROUTED2(GpuStreamTextureMsg_EstablishPeer,
                     int32, /* primary_id */
                     int32  /* secondary_id */)
 
 // Tells the GPU process to set the size of StreamTexture from the given
@@ skipping 303 matching lines @@
 IPC_MESSAGE_ROUTED0(AcceleratedJpegDecoderMsg_Destroy)
 
 //------------------------------------------------------------------------------
 // Accelerated JPEG Decoder Host Messages
 // These messages are sent from the GPU process to Browser process.
 //
 // Report decode status.
 IPC_MESSAGE_ROUTED2(AcceleratedJpegDecoderHostMsg_DecodeAck,
                     int32, /* bitstream_buffer_id */
                     media::JpegDecodeAccelerator::Error /* error */)