[Sync] Register USS types with ModelTypeRegistry before download

components/sync_driver/glue/sync_backend_registrar.cc

Index: components/sync_driver/glue/sync_backend_registrar.cc
diff --git a/components/sync_driver/glue/sync_backend_registrar.cc b/components/sync_driver/glue/sync_backend_registrar.cc
index 0cd87c2d2fb6aa3e6a0c6284876613324db8fa02..cd3170ed561f98a4c997f86599e9e5481183f5b4 100644
--- a/components/sync_driver/glue/sync_backend_registrar.cc
+++ b/components/sync_driver/glue/sync_backend_registrar.cc
@@ -51,6 +51,12 @@ SyncBackendRegistrar::SyncBackendRegistrar(
   DCHECK_GT(workers_.size(), 0u);
 }
 
+void SyncBackendRegistrar::RegisterNonBlockingType(syncer::ModelType type) {
+  DCHECK(routing_info_.find(type) == routing_info_.end() ||
+         routing_info_[type] == syncer::GROUP_NON_BLOCKING);
+  non_blocking_types_.Put(type);
+}
+
 void SyncBackendRegistrar::SetInitialTypes(syncer::ModelTypeSet initial_types) {
   base::AutoLock lock(lock_);
 
@@ -63,7 +69,7 @@ void SyncBackendRegistrar::SetInitialTypes(syncer::ModelTypeSet initial_types) {
   // return correct results.
   for (syncer::ModelTypeSet::Iterator it = initial_types.First(); it.Good();
        it.Inc()) {
-    routing_info_[it.Get()] = syncer::GROUP_PASSIVE;
+    routing_info_[it.Get()] = GetInitialGroupForType(it.Get());
   }
 
   if (!workers_.count(syncer::GROUP_HISTORY)) {
@@ -108,7 +114,7 @@ syncer::ModelTypeSet SyncBackendRegistrar::ConfigureDataTypes(
     // Add a newly specified data type as syncer::GROUP_PASSIVE into the
     // routing_info, if it does not already exist.
     if (routing_info_.count(it.Get()) == 0) {
-      routing_info_[it.Get()] = syncer::GROUP_PASSIVE;
+      routing_info_[it.Get()] = GetInitialGroupForType(it.Get());
       newly_added_types.Put(it.Get());
     }
   }
@@ -280,10 +286,12 @@ bool SyncBackendRegistrar::IsOnThreadForGroup(
     case syncer::GROUP_PASSWORD:
       // TODO(sync): How to check we're on the right thread?
       return type == syncer::PASSWORDS;
-    case syncer::MODEL_SAFE_GROUP_COUNT:
-    default:
+    case syncer::GROUP_NON_BLOCKING:
+      // IsOnThreadForGroup shouldn't be called for non-blocking types.
       return false;
   }
+  NOTREACHED();
+  return false;
 }
 
 SyncBackendRegistrar::~SyncBackendRegistrar() {
@@ -351,4 +359,12 @@ base::Thread* SyncBackendRegistrar::sync_thread() {
   return sync_thread_.get();
 }
 
+syncer::ModelSafeGroup SyncBackendRegistrar::GetInitialGroupForType(
+    syncer::ModelType type) const {
+  if (non_blocking_types_.Has(type))
+    return syncer::GROUP_NON_BLOCKING;
+  else
+    return syncer::GROUP_PASSIVE;
+}
+
 }  // namespace browser_sync