Persist setup metrics and have Chrome report them during UMA upload.

components/metrics/metrics_state_manager.cc

Index: components/metrics/metrics_state_manager.cc
diff --git a/components/metrics/metrics_state_manager.cc b/components/metrics/metrics_state_manager.cc
index 4330839e2af0d6c7ae5bcc8393b65d68d2af8ca8..d2f789f776ad972875cf52e02642e5328476e51c 100644
--- a/components/metrics/metrics_state_manager.cc
+++ b/components/metrics/metrics_state_manager.cc
@@ -200,6 +200,7 @@ void MetricsStateManager::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterInt64Pref(prefs::kMetricsReportingEnabledTimestamp, 0);
   registry->RegisterIntegerPref(prefs::kMetricsLowEntropySource,
                                 kLowEntropySourceNotSet);
+  registry->RegisterInt64Pref(prefs::kSetupMetricsLastSeen, 0);
 
   ClonedInstallDetector::RegisterPrefs(registry);
   CachingPermutedEntropyProvider::RegisterPrefs(registry);