[Sync] ModelTypeStore::ReadMetadataCallback now returns a MetadataBatch

components/sync/device_info/device_info_sync_bridge.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_DEVICE_INFO_DEVICE_INFO_SYNC_BRIDGE_H_
 #define COMPONENTS_SYNC_DEVICE_INFO_DEVICE_INFO_SYNC_BRIDGE_H_
 
 #include <map>
 #include <memory>
 #include <string>
@@ skipping 74 matching lines @@
   void NotifyObservers();
 
   // Used as callback given to LocalDeviceInfoProvider.
   void OnProviderInitialized();
 
   // Methods used as callbacks given to DataTypeStore.
   void OnStoreCreated(ModelTypeStore::Result result,
                       std::unique_ptr<ModelTypeStore> store);
   void OnReadAllData(ModelTypeStore::Result result,
                      std::unique_ptr<ModelTypeStore::RecordList> record_list);
-  void OnReadAllMetadata(
-      ModelTypeStore::Result result,
-      std::unique_ptr<ModelTypeStore::RecordList> metadata_records,
-      const std::string& global_metadata);
+  void OnReadAllMetadata(SyncError error,

[skym, 2016/11/05 00:45:42]

A little bit odd how it has to deal with Result objects on the non-metadata
actions. Is the plan to ultimately convert them all?

We could also just pass the store an error handler object to let it report
things. I'm not sure when the service would want to take action upon error.

[maxbogue, 2016/11/07 17:03:39]

No, the plan is only to change the metadata one. The model type should have
unfiltered access to the data handling but we want to make the metadata handling
as easy as possible.

We could pass an error handler, but then we might have to deal with lifetimes
and such. This is easier for now.

+                         std::unique_ptr<MetadataBatch> metadata_batch);
   void OnCommit(ModelTypeStore::Result result);
 
   // 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();
 
@@ skipping 39 matching lines @@
 
   // Used to update our local device info once every pulse interval.
   base::OneShotTimer pulse_timer_;
 
   DISALLOW_COPY_AND_ASSIGN(DeviceInfoSyncBridge);
 };
 
 }  // namespace syncer
 
 #endif  // COMPONENTS_SYNC_DEVICE_INFO_DEVICE_INFO_SYNC_BRIDGE_H_