Added GPU process "echo" IPC message.

gpu/command_buffer/service/gpu_scheduler_linux.cc

 // 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.
 
 #include "gpu/command_buffer/service/gpu_scheduler.h"
 #include "ui/gfx/gl/gl_context.h"
 #include "ui/gfx/gl/gl_share_group.h"
 #include "ui/gfx/gl/gl_surface.h"
 
 using ::base::SharedMemory;
@@ skipping 40 matching lines @@
                           size,
                           disallowed_extensions,
                           allowed_extensions,
                           attribs);
 }
 
 void GpuScheduler::Destroy() {
   DestroyCommon();
 }
 
-void GpuScheduler::WillSwapBuffers() {
-  if (wrapped_swap_buffers_callback_.get()) {
-    wrapped_swap_buffers_callback_->Run();
-  }
-}
-
 }  // namespace gpu