Fix SyncManager initialization failure crash.

sync/syncable/invalid_directory_backing_store.cc

Index: sync/syncable/invalid_directory_backing_store.cc
diff --git a/sync/syncable/invalid_directory_backing_store.cc b/sync/syncable/invalid_directory_backing_store.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0c522ea3a467e975073df38e393722525042d056
--- /dev/null
+++ b/sync/syncable/invalid_directory_backing_store.cc
@@ -0,0 +1,21 @@
+// 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.
+
+#include "sync/syncable/invalid_directory_backing_store.h"
+
+namespace syncer {
+namespace syncable {
+
+InvalidDirectoryBackingStore::InvalidDirectoryBackingStore()
+    : DirectoryBackingStore("some_fake_user") {
+}
+
+DirOpenResult InvalidDirectoryBackingStore::Load(
+    MetahandlesIndex* entry_bucket,
+    Directory::KernelLoadInfo* kernel_load_info) {
+  return FAILED_OPEN_DATABASE;
+}
+
+}  // namespace syncable
+}  // namespace syncer