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 0e71f3b7de51b940581c102092fe70335001bcc2..dbcd43561327e3cf2961b7464241e8bb942407fb 100644
--- a/sync/internal_api/sync_backup_manager.cc
+++ b/sync/internal_api/sync_backup_manager.cc
@@ -39,6 +39,7 @@ void SyncBackupManager::Init(
   if (SyncRollbackManagerBase::InitInternal(
           database_location,
           internal_components_factory,
+          InternalComponentsFactory::STORAGE_ON_DISK_DEFERRED,
           unrecoverable_error_handler.Pass(),
           report_unrecoverable_error_function)) {
     GetUserShare()->directory->CollectMetaHandleCounts(
@@ -50,10 +51,8 @@ void SyncBackupManager::Init(
 }
 
 void SyncBackupManager::SaveChanges() {
-  if (initialized()) {
+  if (initialized())
     NormalizeEntries();
-    GetUserShare()->directory->SaveChanges();
-  }
 }
 
 SyncStatus SyncBackupManager::GetDetailedStatus() const {
@@ -138,6 +137,15 @@ 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) {}