Let SyncBackupManager keep backup data in memory until shutdown. Only persist

sync/internal_api/sync_backup_manager.cc

Index: sync/internal_api/sync_backup_manager.cc
diff --git a/sync/internal_api/sync_backup_manager.cc b/sync/internal_api/sync_backup_manager.cc
index be8b8720044248a403e928205334745f7d9bacfa..d626229dfc2760cdf888eda04c1b599d0c0ee335 100644
--- a/sync/internal_api/sync_backup_manager.cc
+++ b/sync/internal_api/sync_backup_manager.cc
@@ -23,6 +23,7 @@ void SyncBackupManager::Init(InitArgs* args) {
   if (SyncRollbackManagerBase::InitInternal(
           args->database_location,
           args->internal_components_factory.get(),
+          InternalComponentsFactory::STORAGE_ON_DISK_DEFERRED,
           args->unrecoverable_error_handler.Pass(),
           args->report_unrecoverable_error_function)) {
     GetUserShare()->directory->CollectMetaHandleCounts(
@@ -34,10 +35,8 @@ void SyncBackupManager::Init(InitArgs* args) {
 }
 
 void SyncBackupManager::SaveChanges() {
-  if (initialized()) {
+  if (initialized())
     NormalizeEntries();
-    GetUserShare()->directory->SaveChanges();
-  }
 }
 
 SyncStatus SyncBackupManager::GetDetailedStatus() const {
@@ -122,6 +121,15 @@ void SyncBackupManager::HideSyncPreference(ModelType type) {
   }
 }
 
+void SyncBackupManager::ShutdownOnSyncThread(ShutdownReason reason) {
+  if (reason == SWITCH_MODE_SYNC) {
+    NormalizeEntries();
+    GetUserShare()->directory->SaveChanges();
+  }
+
+  SyncRollbackManagerBase::ShutdownOnSyncThread(reason);
+}
+
 void SyncBackupManager::RegisterDirectoryTypeDebugInfoObserver(
     syncer::TypeDebugInfoObserver* observer) {}