Linux: remove use_system_mesa bits.

third_party/khronos/khronos.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.
 
 {
-  'conditions': [
-    ['use_system_mesa==0', {
-      'targets': [
-        {
-          'target_name': 'khronos_headers',
-          'type': 'none',
-          'all_dependent_settings': {
-            'include_dirs': [
-              '.',
-              '../../gpu',  # Contains GLES2/gl2chromium.h
-            ],
-          },
-        },
-      ],
-    }, { # use_system_mesa==1
-      'targets': [
-        {
-          'target_name': 'khronos_headers',
-          'type': 'none',
-          'variables': {
-            'headers_root_path': '../..',
-            'header_filenames': [
-              'GLES2/gl2.h;<GLES2/gl2chromium.h>;',
-              'GLES2/gl2ext.h;<GLES2/gl2chromium.h>;<GLES2/gl2extchromium.h>',
-            ],
-            'shim_generator_additional_args': [
-              '--headers-root', '.',
-              '--use-include-next',
-            ],
-            'khronos_headers_symlink_source%': '/usr/include',
-            'khronos_headers_symlink_target': '<(SHARED_INTERMEDIATE_DIR)/khronos_symlinks',
-          },
-          'includes': [
-            '../../build/shim_headers.gypi',
-          ],
-          'all_dependent_settings': {
-            'include_dirs': [
-              '<(khronos_headers_symlink_target)',
-              '../../gpu',  # Contains GLES2/gl2chromium.h
-            ],
-          },
-          'actions': [
-            # Symlink system headers into include paths so that nacl
-            # untrusted build can use them. Adding system include paths
-            # to nacl untrusted build include path would break the build,
-            # so we only add needed parts.
-            {
-              'action_name': 'create_khronos_symlinks_gles2',
-              'variables': {
-                'dummy_file':  '<(khronos_headers_symlink_target)/.dummy_gles2',
-              },
-              'inputs': [
-                'khronos.gyp',
-              ],
-              'outputs': [
-                '<(dummy_file)',
-              ],
-              'action': [
-                '../../build/symlink.py',
-                '--force',
-                '--touch', '<(dummy_file)',
-                '<(khronos_headers_symlink_source)/GLES2',
-                '<(khronos_headers_symlink_target)',
-              ],
-              'message': 'Creating GLES2 headers symlinks.',
-            },
-            {
-              'action_name': 'create_khronos_symlinks_khr',
-              'variables': {
-                'dummy_file':  '<(khronos_headers_symlink_target)/.dummy_khr',
-              },
-              'inputs': [
-                'khronos.gyp',
-              ],
-              'outputs': [
-                '<(dummy_file)',
-              ],
-              'action': [
-                '../../build/symlink.py',
-                '--force',
-                '--touch', '<(dummy_file)',
-                '<(khronos_headers_symlink_source)/KHR',
-                '<(khronos_headers_symlink_target)',
-              ],
-              'message': 'Creating KHR headers symlinks.',
-            },
-          ],
-        },
-      ],
-    }],
+  'targets': [
+    {
+      'target_name': 'khronos_headers',
+      'type': 'none',
+      'all_dependent_settings': {
+        'include_dirs': [
+          '.',
+          '../../gpu',  # Contains GLES2/gl2chromium.h
+        ],
+      },
+    },
   ],
 }