Putting histogram names of tracked prefs in tracked_preference_histogram_name file.

components/user_prefs/tracked/pref_names.cc

Index: components/user_prefs/tracked/pref_names.cc
diff --git a/components/user_prefs/tracked/pref_names.cc b/components/user_prefs/tracked/pref_names.cc
index a6c73a65228769269481706d175c8e4edd3d98d0..4762c54b6ae0cc80de5ffd6cb7a687a5df02f09e 100644
--- a/components/user_prefs/tracked/pref_names.cc
+++ b/components/user_prefs/tracked/pref_names.cc
@@ -11,3 +11,25 @@ namespace user_prefs {
 const char kPreferenceResetTime[] = "prefs.preference_reset_time";
 
 }  // namespace user_prefs
+
+namespace user_tracked_prefs {
+
+const char kTrackedPreferenceUnchanged[] =
+    "Settings.TrackedPreferenceUnchanged";
+const char kTrackedPreferenceCleared[] = "Settings.TrackedPreferenceCleared";
+const char kTrackedPreferenceMigratedLegacyDeviceId[] =
+    "Settings.TrackedPreferenceMigratedLegacyDeviceId";
+const char kTrackedPreferenceChanged[] = "Settings.TrackedPreferenceChanged";
+const char kTrackedPreferenceInitialized[] =
+    "Settings.TrackedPreferenceInitialized";
+const char kTrackedPreferenceTrustedInitialized[] =
+    "Settings.TrackedPreferenceTrustedInitialized";
+const char kTrackedPreferenceNullInitialized[] =
+    "Settings.TrackedPreferenceNullInitialized";
+const char kTrackedPreferenceWantedReset[] =
+    "Settings.TrackedPreferenceWantedReset";
+const char kTrackedPreferenceReset[] = "Settings.TrackedPreferenceReset";
+const char kTrackedSplitPreferenceChanged[] =
+    "Settings.TrackedSplitPreferenceChanged.";
+
+}  // namespace user_tracked_prefs.