Add support for GL_CHROMIUM_pixel_transfer_buffer_object.

gpu/gpu.gyp

 # 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.
 
 {
   'variables': {
     'nacl_win64_target': 0,
   },
   'includes': [
     'gpu_common.gypi',
@@ skipping 127 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_interface_stub.cc',
         'command_buffer/client/gles2_interface_stub.h',
         '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',
@@ skipping 281 matching lines @@
           'configurations': {
             'Common_Base': {
               'msvs_target_platform': 'x64',
             },
           },
         },
       ],
     }],
   ],
 }