[Sync] Ensure that CONFIGURE_CLEAN types get unapplied before configuration

components/sync/driver/glue/sync_backend_host_impl.cc

Index: components/sync/driver/glue/sync_backend_host_impl.cc
diff --git a/components/sync/driver/glue/sync_backend_host_impl.cc b/components/sync/driver/glue/sync_backend_host_impl.cc
index b125c4482823f753def6fe15a43af09cb18650f1..4cb9333a100a945610ff1c6de47e5046afa1800f 100644
--- a/components/sync/driver/glue/sync_backend_host_impl.cc
+++ b/components/sync/driver/glue/sync_backend_host_impl.cc
@@ -281,7 +281,8 @@ ModelTypeSet SyncBackendHostImpl::ConfigureDataTypes(
   registrar_->GetModelSafeRoutingInfo(&routing_info);
 
   ModelTypeSet current_types = registrar_->GetLastConfiguredTypes();
-  ModelTypeSet types_to_purge = Difference(ModelTypeSet::All(), current_types);
+  ModelTypeSet types_to_purge = Difference(
+      ModelTypeSet::All(), Difference(current_types, clean_first_types));

[Nicolas Zea, 2016/12/16 22:08:42]

I think it might be simpler to understand if we just insert clean_first_types
into types_to_purge?

[pavely, 2016/12/16 23:57:46]

Done.

   ModelTypeSet inactive_types =
       GetDataTypesInState(CONFIGURE_INACTIVE, config_state_map);
   types_to_purge.RemoveAll(inactive_types);