Fix SyncManager initialization failure crash.

sync/syncable/invalid_directory_backing_store.h

Index: sync/syncable/invalid_directory_backing_store.h
diff --git a/sync/syncable/invalid_directory_backing_store.h b/sync/syncable/invalid_directory_backing_store.h
new file mode 100644
index 0000000000000000000000000000000000000000..2d3991881c840df0ed09ec07414429d9ae31a68a
--- /dev/null
+++ b/sync/syncable/invalid_directory_backing_store.h
@@ -0,0 +1,27 @@
+// Copyright (c) 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.
+
+#ifndef SYNC_SYNCABLE_INVALID_DIRECTORY_BACKING_STORE_H_
+#define SYNC_SYNCABLE_INVALID_DIRECTORY_BACKING_STORE_H_
+
+#include "sync/syncable/directory_backing_store.h"
+
+namespace syncer {
+namespace syncable {
+
+// A class used to test scenarios where loading a directory fails.
+class InvalidDirectoryBackingStore : public DirectoryBackingStore {
+ public:
+  InvalidDirectoryBackingStore();
+  virtual DirOpenResult Load(
+      MetahandlesIndex* entry_bucket,
+      Directory::KernelLoadInfo* kernel_load_info) OVERRIDE;
+ private:
+  DISALLOW_COPY_AND_ASSIGN(InvalidDirectoryBackingStore);
+};
+
+}  // namespace syncable
+}  // namespace syncer
+
+#endif  // SYNC_SYNCABLE_INVALID_DIRECTORY_BACKING_STORE_H_