Added GPU process "echo" IPC message.

gpu/command_buffer/service/gles2_cmd_decoder.h

 // Copyright (c) 2011 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.
 
 // This file contains the GLES2Decoder class.
 
 #ifndef GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_
 #define GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_
 
 #include <vector>
@@ skipping 85 matching lines @@
   virtual gfx::GLContext* GetGLContext() = 0;
 
   // Gets the associated ContextGroup
   virtual ContextGroup* GetContextGroup() = 0;
 
   // Sets a callback which is called when a glResizeCHROMIUM command
   // is processed.
   virtual void SetResizeCallback(
       Callback1<gfx::Size>::Type* callback) = 0;
 
+#if defined(OS_MACOSX)
   // Sets a callback which is called when a SwapBuffers command is processed.
   virtual void SetSwapBuffersCallback(Callback0::Type* callback) = 0;
+#endif
 
   // Get the service texture ID corresponding to a client texture ID.
   // If no such record is found then return false.
   virtual bool GetServiceTextureId(uint32 client_texture_id,
                                    uint32* service_texture_id);
 
   // Provides detail about a lost context if one occurred.
   virtual error::ContextLostReason GetContextLostReason() = 0;
 
  protected:
   GLES2Decoder();
 
  private:
   bool debug_;
 
   DISALLOW_COPY_AND_ASSIGN(GLES2Decoder);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_GLES2_CMD_DECODER_H_