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

sync/internal_api/public/internal_components_factory.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // InternalComponentsFactory exists so that tests can override creation of
 // components used by the SyncManager that are not exposed across the sync
 // API boundary.
 
 #ifndef SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_
 #define SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_
@@ skipping 54 matching lines @@
   // to grow and shrink over time with transient features / experiments,
   // roughly following command line flags in chrome. Implementations of
   // InternalComponentsFactory can use this information to build components
   // with appropriate bells and whistles.
   struct Switches {
     EncryptionMethod encryption_method;
     BackoffOverride backoff_override;
     PreCommitUpdatesPolicy pre_commit_updates_policy;
   };
 
+  // For selecting the types of storage to use to persist sync data when
+  // BuildDirectoryBackingStore() is called.
+  enum StorageOption {
+    // BuildDirectoryBackingStore should not use persistent on-disk storage.
+    STORAGE_IN_MEMORY,
+    // Use this if you want BuildDirectoryBackingStore to create/use a real
+    // on disk store.
+    STORAGE_ON_DISK,
+    // Use this to defer creating on-disk database until
+    // DirectoryBackingStore::SaveChanges() is called.
+    STORAGE_ON_DISK_DEFERRED,
+    // Use this to test the case where a directory fails to load.
+    STORAGE_INVALID
+  };
+
   virtual ~InternalComponentsFactory() {}
 
   virtual scoped_ptr<SyncScheduler> BuildScheduler(
       const std::string& name,
       sessions::SyncSessionContext* context,
       CancelationSignal* cancelation_signal) = 0;
 
   virtual scoped_ptr<sessions::SyncSessionContext> BuildContext(
       ServerConnectionManager* connection_manager,
       syncable::Directory* directory,
       ExtensionsActivity* extensions_activity,
       const std::vector<SyncEngineEventListener*>& listeners,
       sessions::DebugInfoGetter* debug_info_getter,
       ModelTypeRegistry* model_type_registry,
       const std::string& invalidator_client_id) = 0;
 
   virtual scoped_ptr<syncable::DirectoryBackingStore>
   BuildDirectoryBackingStore(
+      StorageOption storage,
       const std::string& dir_name,
       const base::FilePath& backing_filepath) = 0;
 
   // Returns the Switches struct that this object is using as configuration, if
   // the implementation is making use of one.
   virtual Switches GetSwitches() const = 0;
 };
 
 }  // namespace syncer
 
 #endif  // SYNC_INTERNAL_API_PUBLIC_INTERNAL_COMPONENTS_FACTORY_H_