sync: Introduce ModelTypeRegistry and helpers

sync/engine/process_updates_util.cc

Index: sync/engine/process_updates_util.cc
diff --git a/sync/engine/process_updates_util.cc b/sync/engine/process_updates_util.cc
index 49e40b366d05b3ce52db03514a2841fafb0bbe0a..c98ec45fdd4a249483a11f71f67e129e58f3f0f7 100644
--- a/sync/engine/process_updates_util.cc
+++ b/sync/engine/process_updates_util.cc
@@ -76,34 +76,6 @@ bool UpdateContainsNewVersion(syncable::BaseTransaction *trans,
 
 }  // namespace
 
-void PartitionUpdatesByType(
-    const sync_pb::GetUpdatesResponse& updates,
-    ModelTypeSet requested_types,
-    TypeSyncEntityMap* updates_by_type) {
-  int update_count = updates.entries().size();
-  for (ModelTypeSet::Iterator it = requested_types.First();
-       it.Good(); it.Inc()) {
-    updates_by_type->insert(std::make_pair(it.Get(), SyncEntityList()));
-  }
-  for (int i = 0; i < update_count; ++i) {
-    const sync_pb::SyncEntity& update = updates.entries(i);
-    ModelType type = GetModelType(update);
-    if (!IsRealDataType(type)) {
-      NOTREACHED() << "Received update with invalid type.";
-      continue;
-    }
-
-    TypeSyncEntityMap::iterator it = updates_by_type->find(type);
-    if (it == updates_by_type->end()) {
-      DLOG(WARNING) << "Skipping update for unexpected type "
-                    << ModelTypeToString(type);
-      continue;
-    }
-
-    it->second.push_back(&update);
-  }
-}
-
 void ProcessDownloadedUpdates(
     syncable::Directory* dir,
     syncable::ModelNeutralWriteTransaction* trans,