Add targets for mesa to the GN build.

third_party/mesa/mesa.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': {
     'generated_src_dir': 'src/chromium_gensrc',
   },
   'target_defaults': {
     'defines': [
@@ skipping 56 matching lines @@
       ['os_posix == 1 and OS != "android"', {
         'defines': [
           'HAVE_POSIX_MEMALIGN',
         ],
       }],
       ['os_posix == 1 and OS != "mac" and OS != "android"', {
         'cflags': [
           '-fPIC',
         ],
       }],
-      ['OS=="win"', {
-        # Pick up emulation headers not supported by Visual Studio.
-        'include_dirs': [
-          'src/include/c99',
-        ],
-      }],
     ],
   },
   'targets': [
     {
       'target_name': 'mesa_headers',
       'type': 'none',
       'direct_dependent_settings': {
         'include_dirs': [
           'src/include',
         ],
@@ skipping 735 matching lines @@
                 '<(PRODUCT_DIR)/libosmesa.so',
                 '<(SHARED_LIB_DIR)/libosmesa.so',
               ],
             },
           ],
         },
       ],
     }],
   ],
 }