Added switch to disable specified GL extensions.

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 336 matching lines @@
       'defines': [
         'GL_GLEXT_PROTOTYPES',
       ],
       'sources': [
         # Note: sources list duplicated in GN build.
         'command_buffer/tests/compressed_texture_test.cc',
         'command_buffer/tests/gl_bind_uniform_location_unittest.cc',
         'command_buffer/tests/gl_chromium_framebuffer_multisample_unittest.cc',
         'command_buffer/tests/gl_chromium_path_rendering_unittest.cc',
         'command_buffer/tests/gl_clear_framebuffer_unittest.cc',
+        'command_buffer/tests/gl_context_unittest.cc',
         'command_buffer/tests/gl_copy_texture_CHROMIUM_unittest.cc',
         'command_buffer/tests/gl_depth_texture_unittest.cc',
         'command_buffer/tests/gl_gpu_memory_buffer_unittest.cc',
         'command_buffer/tests/gl_lose_context_chromium_unittest.cc',
         'command_buffer/tests/gl_manager.cc',
         'command_buffer/tests/gl_manager.h',
         'command_buffer/tests/gl_pointcoord_unittest.cc',
         'command_buffer/tests/gl_program_unittest.cc',
         'command_buffer/tests/gl_query_unittest.cc',
         'command_buffer/tests/gl_readback_unittest.cc',
@@ skipping 390 matching lines @@
                   '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
                 ],
               }
             ],
           ],
         },
       ],
     }],
   ],
 }