Use more flexible field trial control on resource prefetching for mobile web

chrome/chrome_tests_unit.gypi

 # Copyright 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': {
     'chrome_unit_tests_sources': [
       '../apps/saved_files_service_unittest.cc',
       '../components/autofill/content/renderer/test_password_autofill_agent.cc',
       '../components/autofill/content/renderer/test_password_autofill_agent.h',
       '../components/autofill/content/renderer/test_password_generation_agent.cc',
@@ skipping 563 matching lines @@
       'browser/policy/cloud/user_policy_signin_service_unittest.cc',
       'browser/policy/file_selection_dialogs_policy_handler_unittest.cc',
       'browser/policy/javascript_policy_handler_unittest.cc',
       'browser/policy/managed_bookmarks_policy_handler_unittest.cc',
       'browser/policy/policy_path_parser_unittest.cc',
       'browser/policy/profile_policy_connector_unittest.cc',
       'browser/policy/url_blacklist_manager_unittest.cc',
       'browser/power/process_power_collector_unittest.cc',
       'browser/predictors/autocomplete_action_predictor_table_unittest.cc',
       'browser/predictors/autocomplete_action_predictor_unittest.cc',
+      'browser/predictors/resource_prefetch_common_unittest.cc',
       'browser/predictors/resource_prefetch_predictor_unittest.cc',
       'browser/predictors/resource_prefetch_predictor_tables_unittest.cc',
       'browser/predictors/resource_prefetcher_unittest.cc',
       'browser/prefs/browser_ui_prefs_migrator_unittest.cc',
       'browser/prefs/chrome_pref_service_unittest.cc',
       'browser/prefs/command_line_pref_store_unittest.cc',
       'browser/prefs/incognito_mode_prefs_unittest.cc',
       'browser/prefs/leveldb_pref_store_unittest.cc',
       'browser/prefs/pref_model_associator_unittest.cc',
       'browser/prefs/prefs_syncable_service_unittest.cc',
@@ skipping 2272 matching lines @@
               'dependencies': [
                 '../tools/xdisplaycheck/xdisplaycheck.gyp:xdisplaycheck',
               ],
             }],
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }