Perform glReadPixels with PBOs in the gpu, if PBOs are available.

gpu/command_buffer/build_gles2_cmd_buffer.py

 #!/usr/bin/env python
 # 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.
 
 """code generator for GLES2 command buffers."""
 
 import itertools
 import os
 import os.path
@@ skipping 1890 matching lines @@
         '// it is easier to specify the result going to some specific place\n'
         '// that exactly fits the rectangle of pixels.\n',
     'type': 'Custom',
     'immediate': False,
     'impl_func': False,
     'client_test': False,
     'cmd_args':
         'GLint x, GLint y, GLsizei width, GLsizei height, '
         'GLenumReadPixelFormat format, GLenumReadPixelType type, '
         'uint32 pixels_shm_id, uint32 pixels_shm_offset, '
-        'uint32 result_shm_id, uint32 result_shm_offset',
+        'uint32 result_shm_id, uint32 result_shm_offset, '
+        'GLboolean async',
     'result': ['uint32'],
     'defer_reads': True,
   },
   'RegisterSharedIdsCHROMIUM': {
     'type': 'Custom',
     'decoder_func': 'DoRegisterSharedIdsCHROMIUM',
     'impl_func': False,
     'expectation': False,
     'immediate': False,
     'extension': True,
@@ skipping 5862 matching lines @@
     gen.WriteGLES2Header("../GLES2/gl2chromium_autogen.h")
 
   if gen.errors > 0:
     print "%d errors" % gen.errors
     return 1
   return 0
 
 
 if __name__ == '__main__':
   sys.exit(main(sys.argv[1:]))