implement getBufferSubDataAsync prototype

gpu/command_buffer/client/gles2_trace_implementation_autogen.h

Index: gpu/command_buffer/client/gles2_trace_implementation_autogen.h
diff --git a/gpu/command_buffer/client/gles2_trace_implementation_autogen.h b/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
index 442f6628ba00f42659b8b306ff9e7314215428a2..9277de1fa51705ad31040aff7aa2b635155b3495 100644
--- a/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
+++ b/gpu/command_buffer/client/gles2_trace_implementation_autogen.h
@@ -841,6 +841,9 @@ void ProgramPathFragmentInputGenCHROMIUM(GLuint program,
                                          GLenum genMode,
                                          GLint components,
                                          const GLfloat* coeffs) override;
+void* GetBufferSubDataAsyncCHROMIUM(GLenum target,
+                                    GLintptr offset,
+                                    GLsizeiptr size) override;
 void CoverageModulationCHROMIUM(GLenum components) override;
 GLenum GetGraphicsResetStatusKHR() override;
 void BlendBarrierKHR() override;