Decouple Metrics Initialization from IO Thread Initialization

components/metrics/data_use_tracker_unittest.cc

Index: components/metrics/data_use_tracker_unittest.cc
diff --git a/components/metrics/data_use_tracker_unittest.cc b/components/metrics/data_use_tracker_unittest.cc
index ed32a4a20247e5db211e54c5d21f1b18e8191323..0cb96687bd189ed26a37b110ac3276ec1046e9e2 100644
--- a/components/metrics/data_use_tracker_unittest.cc
+++ b/components/metrics/data_use_tracker_unittest.cc
@@ -109,7 +109,7 @@ TEST(DataUseTrackerTest, CheckUpdateUsagePref) {
   int user_pref_value = 0;
   int uma_pref_value = 0;
 
-  data_use_tracker.UpdateMetricsUsagePrefsOnUIThread("", 2 * 100, true);
+  data_use_tracker.UpdateMetricsUsagePrefs("", 2 * 100, true);
   local_state.GetDictionary(prefs::kUserCellDataUse)
       ->GetInteger(kTodayStr, &user_pref_value);
   EXPECT_EQ(2 * 100, user_pref_value);
@@ -117,7 +117,7 @@ TEST(DataUseTrackerTest, CheckUpdateUsagePref) {
       ->GetInteger(kTodayStr, &uma_pref_value);
   EXPECT_EQ(0, uma_pref_value);
 
-  data_use_tracker.UpdateMetricsUsagePrefsOnUIThread("UMA", 100, true);
+  data_use_tracker.UpdateMetricsUsagePrefs("UMA", 100, true);
   local_state.GetDictionary(prefs::kUserCellDataUse)
       ->GetInteger(kTodayStr, &user_pref_value);
   EXPECT_EQ(3 * 100, user_pref_value);