[Sync] ModelTypeStore::ReadMetadataCallback now returns a MetadataBatch

components/sync/device_info/device_info_sync_bridge.h

Index: components/sync/device_info/device_info_sync_bridge.h
diff --git a/components/sync/device_info/device_info_sync_bridge.h b/components/sync/device_info/device_info_sync_bridge.h
index 35701b7b609603096b83c531452651564551c81c..2cfa1e5a9906cce7b5de464fb5e2d054ebd6e244 100644
--- a/components/sync/device_info/device_info_sync_bridge.h
+++ b/components/sync/device_info/device_info_sync_bridge.h
@@ -92,10 +92,8 @@ class DeviceInfoSyncBridge : public ModelTypeSyncBridge,
                       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.