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 197 matching lines @@
       'type': 'executable',
       'dependencies': [
         'app_shell_lib',
         '<(DEPTH)/base/base.gyp:base',
         '<(DEPTH)/base/base.gyp:test_support_base',
         '<(DEPTH)/content/content.gyp:content_app_both',
         '<(DEPTH)/content/content_shell_and_tests.gyp:test_support_content',
         '<(DEPTH)/extensions/extensions.gyp:extensions_shell_and_test_pak',
         '<(DEPTH)/extensions/extensions.gyp:extensions_test_support',
         '<(DEPTH)/testing/gtest.gyp:gtest',
+        # Only needed at runtime.
+        '../../third_party/mesa/mesa.gyp:osmesa',
       ],
       'sources': [
         '<@(app_shell_unittests_sources)',
       ],
       'conditions': [
         ['disable_nacl==0', {
           'sources': [
             '<@(app_shell_unittests_sources_nacl)',
           ],
         }],
@@ skipping 208 matching lines @@
             '../../build/isolate.gypi',
           ],
           'sources': [
             'app_shell_unittests.isolate',
           ],
         },
       ],
     }],
   ],
 }