Add support for GL_CHROMIUM_pixel_transfer_buffer_object.

gpu/gpu_common.gypi

 # 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.
 
 {
   'targets': [
     {
       # Library emulates GLES2 using command_buffers.
       'target_name': 'gles2_implementation',
       'type': '<(component)',
@@ skipping 122 matching lines @@
         'gpu',
         'gpu_unittest_utils',
         'gles2_implementation_client_side_arrays',
         'gles2_cmd_helper',
       ],
       'defines': [
         'GLES2_C_LIB_IMPLEMENTATION',
       ],
       'sources': [
         '<@(gles2_c_lib_source_files)',
+        'command_buffer/client/buffer_tracker_unittest.cc',
         'command_buffer/client/client_test_helper.cc',
         'command_buffer/client/client_test_helper.h',
         'command_buffer/client/cmd_buffer_helper_test.cc',
         'command_buffer/client/fenced_allocator_test.cc',
         'command_buffer/client/gles2_implementation_unittest.cc',
         'command_buffer/client/mapped_memory_unittest.cc',
         'command_buffer/client/query_tracker_unittest.cc',
         'command_buffer/client/program_info_manager_unittest.cc',
         'command_buffer/client/ring_buffer_test.cc',
         'command_buffer/client/share_group_unittest.cc',
@@ skipping 95 matching lines @@
       ],
       'sources': [
         'command_buffer/common/gl_mock.h',
         'command_buffer/common/gl_mock.cc',
         'command_buffer/service/gles2_cmd_decoder_mock.cc',
         'command_buffer/service/gles2_cmd_decoder_mock.cc',
       ],
     },
   ],
 }