Expose a method in VariationsService to trigger a seed fetch.

chrome/chrome_tests_unit.gypi

Index: chrome/chrome_tests_unit.gypi
diff --git a/chrome/chrome_tests_unit.gypi b/chrome/chrome_tests_unit.gypi
index 5f02088faa8b47d78f1b97e0ffcbcbf805b6189b..1596d1d801b1215c363b75e16ffd1cddaab08a07 100644
--- a/chrome/chrome_tests_unit.gypi
+++ b/chrome/chrome_tests_unit.gypi
@@ -1064,9 +1064,10 @@
         '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',
@@ -2545,6 +2546,7 @@
             'tools/profile_reset/jtl_compiler.gyp:jtl_compiler_lib',
           ],
           'sources!': [
+            'browser/metrics/variations/variations_request_scheduler_mobile_unittest.cc',
             'browser/net/spdyproxy/data_reduction_proxy_settings_unittest.cc',
             'browser/net/spdyproxy/data_reduction_proxy_settings_unittest.h',
             'browser/web_resource/promo_resource_service_mobile_ntp_unittest.cc',