Create Ukm ReportingService implementation.

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 3e3e73c268b45571e597684800343f3fe766ed52..a271b5d4d250a2b3bc4c7526952e92bb46b425d2 100644
--- a/components/metrics/data_use_tracker_unittest.cc
+++ b/components/metrics/data_use_tracker_unittest.cc
@@ -21,10 +21,7 @@ const char kExpiredDateStr2[] = "2016-03-01";
 
 class TestDataUsePrefService : public TestingPrefServiceSimple {
  public:
-  TestDataUsePrefService() {
-    registry()->RegisterDictionaryPref(metrics::prefs::kUserCellDataUse);
-    registry()->RegisterDictionaryPref(metrics::prefs::kUmaCellDataUse);
-  }
+  TestDataUsePrefService() { DataUseTracker::RegisterPrefs(registry()); }
 
   void ClearDataUsePrefs() {
     ClearPref(metrics::prefs::kUserCellDataUse);