Add missing dependencies.

extensions/shell/app_shell.gyp

 # Copyright 2014 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.
 
 {
   'includes': [
     'app_shell.gypi',
   ],
   'variables': {
     # Product name is used for Mac bundle.
@@ skipping 412 matching lines @@
           ],
         },  # target app_shell_helper
       ],
     }],  # OS=="mac"
     ['test_isolation_mode != "noop"', {
       'targets': [
         {
           'target_name': 'app_shell_unittests_run',
           'type': 'none',
           'dependencies': [
+            '../../third_party/mesa/mesa.gyp:osmesa',
             'app_shell_unittests',
           ],
           'includes': [
             '../../build/isolate.gypi',
           ],
           'sources': [
             'app_shell_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }