Expose a method in VariationsService to trigger a seed fetch.

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.
 {
   'targets': [
     {
       # This target contains mocks and test utilities that don't belong in
       # production libraries but are used by more than one test executable.
       'target_name': 'test_support_common',
       'type': 'static_library',
@@ skipping 1044 matching lines @@
         'browser/media_galleries/media_scan_manager_unittest.cc',
         'browser/media_galleries/win/mtp_device_object_enumerator_unittest.cc',
         'browser/metrics/compression_utils_unittest.cc',
         'browser/metrics/metrics_log_unittest.cc',
         'browser/metrics/metrics_log_serializer_unittest.cc',
         'browser/metrics/metrics_reporting_scheduler_unittest.cc',
         'browser/metrics/metrics_service_unittest.cc',
         'browser/metrics/thread_watcher_unittest.cc',
         'browser/metrics/time_ticks_experiment_unittest.cc',
         'browser/metrics/variations/variations_http_header_provider_unittest.cc',
+        'browser/metrics/variations/variations_request_scheduler_mobile_unittest.cc',
+        'browser/metrics/variations/variations_request_scheduler_unittest.cc',
         'browser/metrics/variations/variations_seed_store_unittest.cc',
         'browser/metrics/variations/variations_service_unittest.cc',
-        'browser/metrics/variations/variations_request_scheduler_unittest.cc',
         'browser/net/chrome_fraudulent_certificate_reporter_unittest.cc',
         'browser/net/chrome_network_delegate_unittest.cc',
         'browser/net/client_hints_unittest.cc',
         'browser/net/connection_tester_unittest.cc',
         'browser/net/dns_probe_runner_unittest.cc',
         'browser/net/dns_probe_service_unittest.cc',
         'browser/net/evicted_domain_cookie_counter_unittest.cc',
         'browser/net/firefox_proxy_settings_unittest.cc',
         'browser/net/http_pipelining_compatibility_client_unittest.cc',
         'browser/net/http_server_properties_manager_unittest.cc',
@@ skipping 1845 matching lines @@
             'browser/ui/app_list/test/fake_profile_store.h',
             'browser/ui/app_list/test/fast_show_pickler_unittest.cc',
             'browser/ui/views/app_list/linux/app_list_linux_unittest.cc',
             'browser/ui/views/app_list/win/app_list_win_unittest.cc',
           ],
         },
       ],
     }],
   ],  # 'conditions'
 }