implement getBufferSubDataAsync prototype

gpu/command_buffer/client/gles2_interface_autogen.h

 // Copyright 2014 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
 // It's formatted by clang-format using chromium coding style:
 //    clang-format -i -style=chromium filename
 // DO NOT EDIT!
 
@@ skipping 849 matching lines @@
     GLenum transformType,
     const GLfloat* transformValues) = 0;
 virtual void BindFragmentInputLocationCHROMIUM(GLuint program,
                                                GLint location,
                                                const char* name) = 0;
 virtual void ProgramPathFragmentInputGenCHROMIUM(GLuint program,
                                                  GLint location,
                                                  GLenum genMode,
                                                  GLint components,
                                                  const GLfloat* coeffs) = 0;
+virtual void* GetBufferSubDataAsyncCHROMIUM(GLenum target,
+                                            GLintptr offset,
+                                            GLsizeiptr size) = 0;
 virtual void CoverageModulationCHROMIUM(GLenum components) = 0;
 virtual GLenum GetGraphicsResetStatusKHR() = 0;
 virtual void BlendBarrierKHR() = 0;
 virtual void ApplyScreenSpaceAntialiasingCHROMIUM() = 0;
 virtual void BindFragDataLocationIndexedEXT(GLuint program,
                                             GLuint colorNumber,
                                             GLuint index,
                                             const char* name) = 0;
 virtual void BindFragDataLocationEXT(GLuint program,
                                      GLuint colorNumber,
                                      const char* name) = 0;
 virtual GLint GetFragDataIndexEXT(GLuint program, const char* name) = 0;
 virtual void UniformMatrix4fvStreamTextureMatrixCHROMIUM(
     GLint location,
     GLboolean transpose,
     const GLfloat* transform) = 0;
 virtual void SwapBuffersWithDamageCHROMIUM(GLint x,
                                            GLint y,
                                            GLint width,
                                            GLint height) = 0;
 #endif  // GPU_COMMAND_BUFFER_CLIENT_GLES2_INTERFACE_AUTOGEN_H_