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

sync/internal_api/public/internal_components_factory.h

Index: sync/internal_api/public/internal_components_factory.h
diff --git a/sync/internal_api/public/internal_components_factory.h b/sync/internal_api/public/internal_components_factory.h
index f43804ac4d6aecef6398b5912b9ce0160468315c..f077af006a33b7e026d78d59548f889061d0d58e 100644
--- a/sync/internal_api/public/internal_components_factory.h
+++ b/sync/internal_api/public/internal_components_factory.h
@@ -72,6 +72,21 @@ class SYNC_EXPORT InternalComponentsFactory {
     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(
@@ -90,6 +105,7 @@ class SYNC_EXPORT InternalComponentsFactory {
 
   virtual scoped_ptr<syncable::DirectoryBackingStore>
   BuildDirectoryBackingStore(
+      StorageOption storage,
       const std::string& dir_name,
       const base::FilePath& backing_filepath) = 0;