[Sync] Refactoring polling to be reliable.

components/sync_driver/sync_prefs.cc

Index: components/sync_driver/sync_prefs.cc
diff --git a/components/sync_driver/sync_prefs.cc b/components/sync_driver/sync_prefs.cc
index 89f5320e0bdcda0cff731648e55510ea875e7859..82106eeaeb6cf77584e7993558e63931643b51d8 100644
--- a/components/sync_driver/sync_prefs.cc
+++ b/components/sync_driver/sync_prefs.cc
@@ -38,6 +38,7 @@ void SyncPrefs::RegisterProfilePrefs(
   registry->RegisterBooleanPref(prefs::kSyncHasSetupCompleted, false);
   registry->RegisterBooleanPref(prefs::kSyncSuppressStart, false);
   registry->RegisterInt64Pref(prefs::kSyncLastSyncedTime, 0);
+  registry->RegisterInt64Pref(prefs::kSyncLastPollTime, 0);
   registry->RegisterInt64Pref(prefs::kSyncFirstSyncTime, 0);
 
   // All datatypes are on by default, but this gets set explicitly
@@ -97,6 +98,7 @@ void SyncPrefs::RemoveSyncPrefObserver(SyncPrefObserver* sync_pref_observer) {
 void SyncPrefs::ClearPreferences() {
   DCHECK(CalledOnValidThread());
   pref_service_->ClearPref(prefs::kSyncLastSyncedTime);
+  pref_service_->ClearPref(prefs::kSyncLastPollTime);
   pref_service_->ClearPref(prefs::kSyncHasSetupCompleted);
   pref_service_->ClearPref(prefs::kSyncEncryptionBootstrapToken);
   pref_service_->ClearPref(prefs::kSyncKeystoreEncryptionBootstrapToken);
@@ -148,6 +150,17 @@ void SyncPrefs::SetLastSyncedTime(base::Time time) {
   pref_service_->SetInt64(prefs::kSyncLastSyncedTime, time.ToInternalValue());
 }
 
+base::Time SyncPrefs::GetLastPollTime() const {
+  DCHECK(CalledOnValidThread());
+  return base::Time::FromInternalValue(
+      pref_service_->GetInt64(prefs::kSyncLastSyncedTime));
+}
+
+void SyncPrefs::SetLastPollTime(base::Time time) {
+  DCHECK(CalledOnValidThread());
+  pref_service_->SetInt64(prefs::kSyncLastPollTime, time.ToInternalValue());
+}
+
 bool SyncPrefs::HasKeepEverythingSynced() const {
   DCHECK(CalledOnValidThread());
   return pref_service_->GetBoolean(prefs::kSyncKeepEverythingSynced);