Adding streams to dart:html.

tools/dom/templates/html/dart2js/indexed_db_dart2js.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // DO NOT EDIT
 // Auto-generated dart:svg library.
 
 library indexed_db;
 
+import 'dart:async';
 import 'dart:html';
 import 'dart:html_common';
 
 $!GENERATED_DART_FILES
 
 class _KeyRangeFactoryProvider {
 
   static KeyRange createKeyRange_only(/*Key*/ value) =>
       _only(_class(), _translateKey(value));
 
@@ skipping 99 matching lines @@
 
 /// May modify original.  If so, action is idempotent.
 _convertNativeToDart_IDBAny(object) {
   return convertNativeToDart_AcceptStructuredClone(object, mustCopy: false);
 }
 
 
 const String _idbKey = '=List|=Object|num|String';  // TODO(sra): Add Date.
 const _annotation_Creates_IDBKey = const Creates(_idbKey);
 const _annotation_Returns_IDBKey = const Returns(_idbKey);