Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

content/common/gpu/client/webgraphicscontext3d_command_buffer_impl.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/webgraphicscontext3d_command_buffer_impl.h"
 
 #include "third_party/khronos/GLES2/gl2.h"
 #ifndef GL_GLEXT_PROTOTYPES
 #define GL_GLEXT_PROTOTYPES 1
 #endif
@@ skipping 438 matching lines @@
     bool visible) {
   gl_->Flush();
   visible_ = visible;
   context_->SetSurfaceVisible(visible);
   if (!visible)
     gl_->FreeEverything();
 }
 
 void WebGraphicsContext3DCommandBufferImpl::discardFramebufferEXT(
     WGC3Denum target, WGC3Dsizei numAttachments, const WGC3Denum* attachments) {
-  gl_->Flush();
-  context_->DiscardBackbuffer();
+  gl_->DiscardBackbufferCHROMIUM();
 }
 
 void WebGraphicsContext3DCommandBufferImpl::ensureFramebufferCHROMIUM() {
-  gl_->Flush();
-  context_->EnsureBackbuffer();
+  gl_->EnsureBackbufferCHROMIUM();
 }
 
 void WebGraphicsContext3DCommandBufferImpl::
     setMemoryAllocationChangedCallbackCHROMIUM(
         WebGraphicsMemoryAllocationChangedCallbackCHROMIUM* callback) {
   memory_allocation_changed_callback_ = callback;
 }
 
 
 void WebGraphicsContext3DCommandBufferImpl::copyTextureToParentTextureCHROMIUM(
@@ skipping 786 matching lines @@
     swap_client_->OnViewContextSwapBuffersAborted();
 }
 
 void WebGraphicsContext3DCommandBufferImpl::OnErrorMessage(
     const std::string& message, int id) {
   if (error_message_callback_) {
     WebKit::WebString str = WebKit::WebString::fromUTF8(message.c_str());
     error_message_callback_->onErrorMessage(str, id);
   }
 }
-