use getter for databaseId

packages/firestore/src/remote/datastore.ts

@@ -17,6 +17,7 @@
 
 import { CredentialsProvider } from '../api/credentials';
 import { User } from '../auth/user';
+import { DatabaseId } from '../core/database_info';
 import { Query, queryToTarget } from '../core/query';
 import { Document } from '../model/document';
 import { DocumentKey } from '../model/document_key';
@@ -59,7 +60,7 @@ import {
  */
 export abstract class Datastore {
   abstract terminate(): void;
-  abstract serializer: JsonProtoSerializer;
+  abstract databaseId: DatabaseId;
 }
 
 /**
@@ -78,6 +79,10 @@ class DatastoreImpl extends Datastore {
     super();
   }
 
+  get databaseId(): DatabaseId { 
+    return this.serializer.databaseId
+  }
+
   verifyInitialized(): void {
     debugAssert(!!this.connection, 'Datastore.start() not called');
     if (this.terminated) {

packages/firestore/src/remote/remote_store.ts

@@ -378,7 +378,7 @@ function startWatchStream(remoteStoreImpl: RemoteStoreImpl): void {
       getTargetDataForTarget: targetId =>
         remoteStoreImpl.listenTargets.get(targetId) || null
     },
-    remoteStoreImpl.datastore.serializer.databaseId
+    remoteStoreImpl.datastore.databaseId
   );
   ensureWatchStream(remoteStoreImpl).start();
   remoteStoreImpl.onlineStateTracker.handleWatchStreamStart();