Move UKM preferences to incognito persietent list.

Preferences related to UKM are moved to the persistent storage list
for incognito mode.
This CL does not change any current behaviore.

Bug: 861722
Change-Id: I80e3ab0ef4326e7e6105649c3fe376be1755c755
Reviewed-on: https://chromium-review.googlesource.com/1166826Reviewed-by: Steven Holte <holte@chromium.org>
Commit-Queue: Ramin Halavati <rhalavati@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582508}

chrome/browser/prefs/pref_service_incognito_whitelist.cc

@@ -137,6 +137,12 @@ const char* persistent_pref_names[] = {
     metrics::prefs::kUninstallMetricsUptimeSec, metrics::prefs::kUkmCellDataUse,
     metrics::prefs::kUmaCellDataUse, metrics::prefs::kUserCellDataUse,
 
+    // Although UKMs are not collected in incognito, theses preferences may be
+    // changed by UMA/Sync/Unity consent, and need to be the same between
+    // incognito and regular modes.
+    ukm::prefs::kUkmClientId, ukm::prefs::kUkmPersistedLogs,
+    ukm::prefs::kUkmSessionId,
+
     // Variations preferences maybe changed from incognito mode and should be
     // kept in sync between incognito and regular modes.
     variations::prefs::kVariationsCompressedSeed,
@@ -819,10 +825,6 @@ const char* temporary_incognito_whitelist[] = {
     suggestions::prefs::kSuggestionsBlacklist,
     suggestions::prefs::kSuggestionsData,
 
-    // components/ukm/ukm_pref_names.h
-    ukm::prefs::kUkmClientId, ukm::prefs::kUkmPersistedLogs,
-    ukm::prefs::kUkmSessionId,
-
     // components/unified_consent/pref_names.h
     unified_consent::prefs::kUnifiedConsentGiven,
     unified_consent::prefs::kUnifiedConsentMigrationState,