Remove =List in JS, use JSExtendableArray instead.

sdk/lib/html/dart2js/html_dart2js.dart

 /// The Dart HTML library.
 library dart.dom.html;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:_collection-dev' hide Symbol;
 import 'dart:html_common';
 import 'dart:indexed_db';
 import 'dart:isolate';
 import 'dart:json' as json;
 import 'dart:math';
 import 'dart:mdv_observe_impl';
 import 'dart:typed_data';
 import 'dart:svg' as svg;
 import 'dart:web_audio' as web_audio;
 import 'dart:web_gl' as gl;
 import 'dart:web_sql';
 import 'dart:_js_helper' show convertDartClosureToJS, Creates, JavaScriptIndexingBehavior, JSName, Null, Returns;
-import 'dart:_interceptors' show Interceptor;
+import 'dart:_interceptors' show Interceptor, JSExtendableArray; 
 import 'dart:_isolate_helper' show IsolateNatives;
 import 'dart:_foreign_helper' show JS;
 // 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 - unless you are editing documentation as per:
 // https://code.google.com/p/dart/wiki/ContributingHTMLDocumentation
 // Auto-generated dart:html library.
 
@@ skipping 11953 matching lines @@
    * The data could be in the
    * form of a [String], [ArrayBuffer], [Document], [Blob], or json (also a
    * [String]). `null` indicates request failure.
    */
   @DomName('XMLHttpRequest.response')
   @DocsEditable
   @SupportedBrowser(SupportedBrowser.CHROME)
   @SupportedBrowser(SupportedBrowser.FIREFOX)
   @SupportedBrowser(SupportedBrowser.IE, '10')
   @SupportedBrowser(SupportedBrowser.SAFARI)
-  @Creates('ByteBuffer|Blob|Document|=Object|=List|String|num')
+  @Creates('ByteBuffer|Blob|Document|=Object|JSExtendableArray|String|num')
   final Object response;
 
   /**
    * The response in string form or `null on failure.
    */
   @DomName('XMLHttpRequest.responseText')
   @DocsEditable
   final String responseText;
 
   /**
@@ skipping 3118 matching lines @@
   @Unstable
   final String lastEventId;
 
   @DomName('MessageEvent.origin')
   @DocsEditable
   final String origin;
 
   @DomName('MessageEvent.ports')
   @DocsEditable
   @Unstable
-  @Creates('=List')
+  @Creates('JSExtendableArray')
   final List<MessagePort> ports;
 
   WindowBase get source => _convertNativeToDart_Window(this._get_source);
   @JSName('source')
   @DomName('MessageEvent.source')
   @DocsEditable
   @Creates('Window|=Object')
   @Returns('Window|=Object')
   final dynamic _get_source;
 
@@ skipping 14454 matching lines @@
       _position = nextPosition;
       return true;
     }
     _current = null;
     _position = _array.length;
     return false;
   }
 
   T get current => _current;
 }