Add a second unsafe ES3 API in command buffer.

gpu/command_buffer/cmd_buffer_functions.txt

 // 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 read by build_gles2_cmd_buffer.py to generate commands.
 
 GL_APICALL void         GL_APIENTRY glActiveTexture (GLenum texture);
 GL_APICALL void         GL_APIENTRY glAttachShader (GLidProgram program, GLidShader shader);
 GL_APICALL void         GL_APIENTRY glBindAttribLocation (GLidProgram program, GLuint index, const char* name);
 GL_APICALL void         GL_APIENTRY glBindBuffer (GLenumBufferTarget target, GLidBindBuffer buffer);
 GL_APICALL void         GL_APIENTRY glBindFramebuffer (GLenumFrameBufferTarget target, GLidBindFramebuffer framebuffer);
 GL_APICALL void         GL_APIENTRY glBindRenderbuffer (GLenumRenderBufferTarget target, GLidBindRenderbuffer renderbuffer);
 GL_APICALL void         GL_APIENTRY glBindTexture (GLenumTextureBindTarget target, GLidBindTexture texture);
 GL_APICALL void         GL_APIENTRY glBlendColor (GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha);
 GL_APICALL void         GL_APIENTRY glBlendEquation ( GLenumEquation mode );
 GL_APICALL void         GL_APIENTRY glBlendEquationSeparate (GLenumEquation modeRGB, GLenumEquation modeAlpha);
 GL_APICALL void         GL_APIENTRY glBlendFunc (GLenumSrcBlendFactor sfactor, GLenumDstBlendFactor dfactor);
 GL_APICALL void         GL_APIENTRY glBlendFuncSeparate (GLenumSrcBlendFactor srcRGB, GLenumDstBlendFactor dstRGB, GLenumSrcBlendFactor srcAlpha, GLenumDstBlendFactor dstAlpha);
 GL_APICALL void         GL_APIENTRY glBufferData (GLenumBufferTarget target, GLsizeiptr size, const void* data, GLenumBufferUsage usage);
 GL_APICALL void         GL_APIENTRY glBufferSubData (GLenumBufferTarget target, GLintptrNotNegative offset, GLsizeiptr size, const void* data);
 GL_APICALL GLenum       GL_APIENTRY glCheckFramebufferStatus (GLenumFrameBufferTarget target);
 GL_APICALL void         GL_APIENTRY glClear (GLbitfield mask);
 GL_APICALL void         GL_APIENTRY glClearColor (GLclampf red, GLclampf green, GLclampf blue, GLclampf alpha);
 GL_APICALL void         GL_APIENTRY glClearDepthf (GLclampf depth);
 GL_APICALL void         GL_APIENTRY glClearStencil (GLint s);
 GL_APICALL void         GL_APIENTRY glColorMask (GLboolean red, GLboolean green, GLboolean blue, GLboolean alpha);
 GL_APICALL void         GL_APIENTRY glCompileShader (GLidShader shader);
 GL_APICALL void         GL_APIENTRY glCompressedTexImage2D (GLenumTextureTarget target, GLint level, GLenumCompressedTextureFormat internalformat, GLsizei width, GLsizei height, GLintTextureBorder border, GLsizei imageSize, const void* data);
 GL_APICALL void         GL_APIENTRY glCompressedTexSubImage2D (GLenumTextureTarget target, GLint level, GLint xoffset, GLint yoffset, GLsizei width, GLsizei height, GLenumCompressedTextureFormat format, GLsizei imageSize, const void* data);
+GL_APICALL void         GL_APIENTRY glCopyBufferSubData (GLenumBufferTarget readtarget, GLenumBufferTarget writetarget, GLintptrNotNegative readoffset, GLintptrNotNegative writeoffset, GLsizeiptr size);
 GL_APICALL void         GL_APIENTRY glCopyTexImage2D (GLenumTextureTarget target, GLint level, GLenumTextureInternalFormat internalformat, GLint x, GLint y, GLsizei width, GLsizei height, GLintTextureBorder border);
 GL_APICALL void         GL_APIENTRY glCopyTexSubImage2D (GLenumTextureTarget target, GLint level, GLint xoffset, GLint yoffset, GLint x, GLint y, GLsizei width, GLsizei height);
 GL_APICALL GLuint       GL_APIENTRY glCreateProgram (void);
 GL_APICALL GLuint       GL_APIENTRY glCreateShader (GLenumShaderType type);
 GL_APICALL void         GL_APIENTRY glCullFace (GLenumFaceType mode);
 GL_APICALL void         GL_APIENTRY glDeleteBuffers (GLsizeiNotNegative n, const GLuint* buffers);
 GL_APICALL void         GL_APIENTRY glDeleteFramebuffers (GLsizeiNotNegative n, const GLuint* framebuffers);
 GL_APICALL void         GL_APIENTRY glDeleteProgram (GLidProgram program);
 GL_APICALL void         GL_APIENTRY glDeleteRenderbuffers (GLsizeiNotNegative n, const GLuint* renderbuffers);
 GL_APICALL void         GL_APIENTRY glDeleteShader (GLidShader shader);
@@ skipping 184 matching lines @@
 GL_APICALL void         GL_APIENTRY glDrawBuffersEXT (GLsizei count, const GLenum* bufs);
 GL_APICALL void         GL_APIENTRY glDiscardBackbufferCHROMIUM (void);
 GL_APICALL void         GL_APIENTRY glScheduleOverlayPlaneCHROMIUM (GLint plane_z_order, GLenum plane_transform, GLuint overlay_texture_id, GLint bounds_x, GLint bounds_y, GLint bounds_width, GLint bounds_height, GLfloat uv_x, GLfloat uv_y, GLfloat uv_width, GLfloat uv_height);
 
 // Extension CHROMIUM_path_rendering.
 GL_APICALL void         GL_APIENTRY glMatrixLoadfCHROMIUM (GLenumMatrixMode matrixMode, const GLfloat* m);
 GL_APICALL void         GL_APIENTRY glMatrixLoadIdentityCHROMIUM (GLenumMatrixMode matrixMode);
 
 // Extension KHR_blend_equation_advanced
 GL_APICALL void GL_APIENTRY glBlendBarrierKHR (void);