Add user_prefs::TestPrefServiceSyncable

components/pref_registry.gypi

 # Copyright (c) 2013 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.
 
 {
   'targets': [
     {
       'target_name': 'pref_registry',
       'type': '<(component)',
       'dependencies': [
         '../base/base.gyp:base',
         '../base/base.gyp:base_prefs',
         '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
         '../ui/base/ui_base.gyp:ui_base',
       ],
       'include_dirs': [
         '..',
       ],
       'defines': [
         'PREF_REGISTRY_IMPLEMENTATION',
       ],
       'sources': [
         'pref_registry/pref_registry_export.h',
         'pref_registry/pref_registry_syncable.cc',
         'pref_registry/pref_registry_syncable.h',
       ],
     },
+    {
+      'target_name': 'pref_registry_test_support',
+      'type': 'static_library',
+      'dependencies': [
+        'pref_registry',
+      ],
+      'include_dirs': [
+        '..',
+      ],
+      'sources': [
+        'pref_registry/testing_pref_service_syncable.cc',
+        'pref_registry/testing_pref_service_syncable.h',
+      ],
+    },
   ],
 }