Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

content/common/gpu/client/content_gl_context.cc

 // 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.
 
 #include "content/common/gpu/client/content_gl_context.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/lazy_instance.h"
 #include "base/memory/ref_counted.h"
@@ skipping 261 matching lines @@
 }
 
 int ContentGLContext::GetContextID() {
   return command_buffer_->GetRouteID();
 }
 
 bool ContentGLContext::SetSurfaceVisible(bool visible) {
   return GetCommandBufferProxy()->SetSurfaceVisible(visible);
 }
 
-bool ContentGLContext::DiscardBackbuffer() {
-  return GetCommandBufferProxy()->DiscardBackbuffer();
-}
-
-bool ContentGLContext::EnsureBackbuffer() {
-  return GetCommandBufferProxy()->EnsureBackbuffer();
-}
-
 void ContentGLContext::SetMemoryAllocationChangedCallback(
     const base::Callback<void(const GpuMemoryAllocationForRenderer&)>&
         callback) {
   GetCommandBufferProxy()->SetMemoryAllocationChangedCallback(callback);
 }
 
 gpu::gles2::GLES2Implementation* ContentGLContext::GetImplementation() {
   return gles2_implementation_;
 }
 
@@ skipping 171 matching lines @@
 void ContentGLContext::OnContextLost() {
   if (!context_lost_callback_.is_null()) {
     ContentGLContext::ContextLostReason reason = kUnknown;
     if (command_buffer_) {
       reason = ConvertReason(
           command_buffer_->GetLastState().context_lost_reason);
     }
     context_lost_callback_.Run(reason);
   }
 }