Implement client side PBOs for glReadPixel

ui/gl/gl_bindings.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.
 
 #ifndef UI_GL_GL_BINDINGS_H_
 #define UI_GL_GL_BINDINGS_H_
 
 // Includes the platform independent and platform dependent GL headers.
 // Only include this in cc files. It pulls in system headers, including
 // the X11 headers on linux, which define all kinds of macros that are
@@ skipping 133 matching lines @@
 #endif
 
 // GL_OES_compressed_ETC1_RGB8_texture
 #define GL_ETC1_RGB8_OES                                 0x8D64
 
 // GL_OES_vertex_array_object
 #define GL_VERTEX_ARRAY_BINDING_OES                      0x85B5
 
 // GL_CHROMIUM_pixel_transfer_buffer_object
 #define GL_PIXEL_UNPACK_TRANSFER_BUFFER_CHROMIUM         0x78EC
+#define GL_PIXEL_PACK_TRANSFER_BUFFER_CHROMIUM           0x78ED
+#define GL_PIXEL_PACK_TRANSFER_BUFFER_BINDING_CHROMIUM   0x78EE
 #define GL_PIXEL_UNPACK_TRANSFER_BUFFER_BINDING_CHROMIUM 0x78EF
 
 /* GL_EXT_discard_framebuffer */
 #ifndef GL_EXT_discard_framebuffer
 #define GL_COLOR_EXT                                     0x1800
 #define GL_DEPTH_EXT                                     0x1801
 #define GL_STENCIL_EXT                                   0x1802
 #endif
 
 // GL_ARB_get_program_binary
@@ skipping 66 matching lines @@
 GL_EXPORT extern DriverEGL g_driver_egl;
 
 #endif
 
 // Find an entry point to the mock GL implementation.
 void* GL_BINDING_CALL GetMockGLProcAddress(const char* name);
 
 }  // namespace gfx
 
 #endif  // UI_GL_GL_BINDINGS_H_