[SyncFS] Retry initialization of MetadataDatabase on failure of loading ServiceMetadata

chrome/browser/sync_file_system/drive_backend/metadata_database_index.cc

 // Copyright 2014 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 "chrome/browser/sync_file_system/drive_backend/metadata_database_index.h"
 
 #include "base/metrics/histogram.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
@@ skipping 186 matching lines @@
 }
 
 }  // namespace
 
 // static
 scoped_ptr<MetadataDatabaseIndex>
 MetadataDatabaseIndex::Create(LevelDBWrapper* db) {
   DCHECK(db);
 
   scoped_ptr<ServiceMetadata> service_metadata = InitializeServiceMetadata(db);
+  if (!service_metadata)
+    return scoped_ptr<MetadataDatabaseIndex>();
+
   DatabaseContents contents;
-
   PutVersionToDB(kCurrentDatabaseVersion, db);
   ReadDatabaseContents(db, &contents);
   RemoveUnreachableItems(&contents,
                          service_metadata->sync_root_tracker_id(),
                          db);
 
   scoped_ptr<MetadataDatabaseIndex> index(new MetadataDatabaseIndex(db));
   index->Initialize(service_metadata.Pass(), &contents);
   return index.Pass();
 }
@@ skipping 522 matching lines @@
 
     DVLOG(3) << "  Remove from dirty_trackers_: " << tracker_id;
     dirty_trackers_.erase(tracker_id);
 
     demoted_dirty_trackers_.erase(tracker_id);
   }
 }
 
 }  // namespace drive_backend
 }  // namespace sync_file_system