[Sync] WorkerEntityTracker: Ensure that update and commit response have valid id.

components/sync/engine_impl/model_type_worker.cc

Index: components/sync/engine_impl/model_type_worker.cc
diff --git a/components/sync/engine_impl/model_type_worker.cc b/components/sync/engine_impl/model_type_worker.cc
index 85730ed3b7576c6c4b9223ce4feac4ee143459be..de5b19d8e4bcc4e4b7ee2549dd92684c7bd21b98 100644
--- a/components/sync/engine_impl/model_type_worker.cc
+++ b/components/sync/engine_impl/model_type_worker.cc
@@ -347,7 +347,7 @@ void ModelTypeWorker::AdjustCommitProto(sync_pb::SyncEntity* sync_entity) {
 
   // Initial commits need our help to generate a client ID.
   if (sync_entity->version() == kUncommittedVersion) {
-    DCHECK(!sync_entity->has_id_string());
+    DCHECK(sync_entity->id_string().empty());
     // TODO(crbug.com/516866): This is incorrect for bookmarks for two reasons:
     // 1) Won't be able to match previously committed bookmarks to the ones
     //    with server ID.
@@ -358,7 +358,7 @@ void ModelTypeWorker::AdjustCommitProto(sync_pb::SyncEntity* sync_entity) {
     sync_entity->set_id_string(base::GenerateGUID());
     sync_entity->set_version(0);
   } else {
-    DCHECK(sync_entity->has_id_string());
+    DCHECK(!sync_entity->id_string().empty());
   }
 
   // Encrypt the specifics and hide the title if necessary.