Implement Discard and EnsureBackbufferCHROMIUM using command buffer instead of IPC.

gpu/command_buffer/client/gles2_c_lib_autogen.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.
 
 // This file is auto-generated from
 // gpu/command_buffer/build_gles2_cmd_buffer.py
 // DO NOT EDIT!
 
 // These functions emulate GLES2 over command buffers.
 #ifndef GPU_COMMAND_BUFFER_CLIENT_GLES2_C_LIB_AUTOGEN_H_
@@ skipping 618 matching lines @@
 }
 void GLES2DrawElementsInstancedANGLE(
     GLenum mode, GLsizei count, GLenum type, const void* indices,
     GLsizei primcount) {
   gles2::GetGLContext()->DrawElementsInstancedANGLE(
       mode, count, type, indices, primcount);
 }
 void GLES2VertexAttribDivisorANGLE(GLuint index, GLuint divisor) {
   gles2::GetGLContext()->VertexAttribDivisorANGLE(index, divisor);
 }
+void GLES2DiscardBackbufferCHROMIUM() {
+  gles2::GetGLContext()->DiscardBackbufferCHROMIUM();
+}
+void GLES2EnsureBackbufferCHROMIUM() {
+  gles2::GetGLContext()->EnsureBackbufferCHROMIUM();
+}
 
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_C_LIB_AUTOGEN_H_