[Sync] DeviceInfo implementation of MergeSyncData.

sync/api/model_type_service.h

Index: sync/api/model_type_service.h
diff --git a/sync/api/model_type_service.h b/sync/api/model_type_service.h
index 469ed4ad16ea5a1283094a5fa7366637f11993be..996060d171608fecbe8199bc70cc52bbc48ef851 100644
--- a/sync/api/model_type_service.h
+++ b/sync/api/model_type_service.h
@@ -39,7 +39,12 @@ class SYNC_EXPORT ModelTypeService {
   virtual scoped_ptr<MetadataChangeList> CreateMetadataChangeList() = 0;
 
   // Perform the initial merge of data from the sync server. Should only need
-  // to be called when sync is first turned on, not on every restart.
+  // to be called when sync is first turned on, not on every restart. An attempt

[skym, 2016/02/23 20:53:28]

This comment also needs to include:
* What the keys are in the map, how they were created.
* The order persistent writes needs to occur in should they not be done
atomically.

[skym, 2016/03/04 20:28:10]

Done.

+  // should be made to match sync data to local data. Any local pieces of data
+  // that are not present in sync should immediately be Put to the processor
+  // before returning. The same MetadataChangeList that was passed into this
+  // function can be passed to Put calls. Delete can also be called but should
+  // not be needed for most model types.
   virtual syncer::SyncError MergeSyncData(
       scoped_ptr<MetadataChangeList> metadata_change_list,
       EntityDataList entity_data_list) = 0;