Add BackupRollbackController for starting backup/rollback

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 9d34236c62de7791b11baab19ddaea5a51a66f97..2a6c73f416b5d1dcdccb241edc919005b9cc1b51 100644
--- a/components/sync_driver/sync_prefs.cc
+++ b/components/sync_driver/sync_prefs.cc
@@ -29,6 +29,8 @@ SyncPrefs::SyncPrefs(PrefService* pref_service) : pref_service_(pref_service) {
       base::Bind(&SyncPrefs::OnSyncManagedPrefChanged, base::Unretained(this)));
 }
 
+SyncPrefs::SyncPrefs() : pref_service_(NULL) {}
+
 SyncPrefs::~SyncPrefs() { DCHECK(CalledOnValidThread()); }
 
 // static
@@ -135,6 +137,10 @@ void SyncPrefs::RegisterProfilePrefs(
   registry->RegisterListPref(prefs::kSyncAcknowledgedSyncTypes,
                              syncer::ModelTypeSetToValue(model_set),
                              user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
+
+  registry->RegisterIntegerPref(
+      prefs::kSyncRemainingRollbackTries, 0,
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
 
 void SyncPrefs::AddSyncPrefObserver(SyncPrefObserver* sync_pref_observer) {
@@ -365,6 +371,14 @@ void SyncPrefs::AcknowledgeSyncedTypes(syncer::ModelTypeSet types) {
   pref_service_->Set(prefs::kSyncAcknowledgedSyncTypes, *value);
 }
 
+int SyncPrefs::GetRemainingRollbackTries() const {
+  return pref_service_->GetInteger(prefs::kSyncRemainingRollbackTries);
+}
+
+void SyncPrefs::SetRemainingRollbackTries(int times) {
+  pref_service_->SetInteger(prefs::kSyncRemainingRollbackTries, times);
+}
+
 void SyncPrefs::OnSyncManagedPrefChanged() {
   DCHECK(CalledOnValidThread());
   FOR_EACH_OBSERVER(SyncPrefObserver,