[Sync] USS: Fix race condition in DeviceInfoService + add error handling

components/sync_driver/device_info_service.h

 // Copyright 2015 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 COMPONENTS_SYNC_DRIVER_DEVICE_INFO_SERVICE_H_
 #define COMPONENTS_SYNC_DRIVER_DEVICE_INFO_SERVICE_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 101 matching lines @@
                       std::unique_ptr<syncer_v2::ModelTypeStore> store);
   void OnReadAllData(
       syncer_v2::ModelTypeStore::Result result,
       std::unique_ptr<syncer_v2::ModelTypeStore::RecordList> record_list);
   void OnReadAllMetadata(
       syncer_v2::ModelTypeStore::Result result,
       std::unique_ptr<syncer_v2::ModelTypeStore::RecordList> metadata_records,
       const std::string& global_metadata);
   void OnCommit(syncer_v2::ModelTypeStore::Result result);
 
-  // Checks if conditions have been met to perform reconciliation between the
-  // locally provide device info and the stored device info data. If conditions
-  // are met and the sets of data differ, than we condier this a local change
-  // and we send it to the processor.
-  void TryReconcileLocalAndStored();
+  // Load metadata if the data is loaded and the provider is initialized.
+  void LoadMetadataIfReady();
+
+  // Performs reconciliation between the locally provided device info and the
+  // stored device info data. If the sets of data differ, then we consider this
+  // a local change and we send it to the processor.
+  void ReconcileLocalAndStored();
 
   // Stores the updated version of the local copy of device info in durable
   // storage, in memory, and informs sync of the change. Should not be called
   // before the provider and processor have initialized.
   void SendLocalData();
 
   // Persists the changes in the given aggregators and notifies observers if
   // indicated to do as such.
   void CommitAndNotify(
       std::unique_ptr<syncer_v2::ModelTypeStore::WriteBatch> batch,
       std::unique_ptr<syncer_v2::MetadataChangeList> metadata_change_list,
       bool should_notify);
 
   // Counts the number of active devices relative to |now|. The activeness of a
   // device depends on the amount of time since it was updated, which means
   // comparing it against the current time. |now| is passed into this method to
   // allow unit tests to control expected results.
   int CountActiveDevices(const base::Time now) const;
 
+  // Report an error starting up to sync if it tries to connect to this
+  // datatype, since these errors prevent us from knowing if sync is enabled.
+  void ReportStartupErrorToSync(const std::string& msg);
+
   // Find the timestamp for the last time this |device_info| was edited.
   static base::Time GetLastUpdateTime(
       const sync_pb::DeviceInfoSpecifics& specifics);
 
   // |local_device_info_provider_| isn't owned.
   const sync_driver::LocalDeviceInfoProvider* const local_device_info_provider_;
 
   ClientIdToSpecifics all_data_;
 
   // Registered observers, not owned.
   base::ObserverList<Observer, true> observers_;
 
   // Used to listen for provider initialization. If the provider is already
   // initialized during our constructor then the subscription is never used.
   std::unique_ptr<sync_driver::LocalDeviceInfoProvider::Subscription>
       subscription_;
 
   // In charge of actually persiting changes to disk, or loading previous data.
   std::unique_ptr<syncer_v2::ModelTypeStore> store_;
 
   // If |local_device_info_provider_| has initialized.
   bool has_provider_initialized_ = false;
+  // If data has been loaded from the store.
+  bool has_data_loaded_ = false;
   // if |change_processor()| has been given metadata.
   bool has_metadata_loaded_ = false;
 
   // Used to update our local device info once every pulse interval.
   base::OneShotTimer pulse_timer_;
 
   // Should always be last member.
   base::WeakPtrFactory<DeviceInfoService> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DeviceInfoService);
 };
 
 }  // namespace sync_driver_v2
 
 #endif  // COMPONENTS_SYNC_DRIVER_DEVICE_INFO_SERVICE_H_