Make new StreamController be async by default.

tools/dom/src/KeyboardEventStream.dart

 // 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.
 
 part of html;
 
 /**
  * Internal class that does the actual calculations to determine keyCode and
  * charCode for keydown, keypress, and keyup events for all browsers.
  */
@@ skipping 10 matching lines @@
   /** The type of KeyEvent we are tracking (keyup, keydown, keypress). */
   final String _type;
 
   /** The element we are watching for events to happen on. */
   final EventTarget _target;
 
   // The distance to shift from upper case alphabet Roman letters to lower case.
   static final int _ROMAN_ALPHABET_OFFSET = "a".codeUnits[0] - "A".codeUnits[0];
 
   /** Controller to produce KeyEvents for the stream. */
-  final StreamController _controller = new StreamController();
+  final StreamController _controller = new StreamController(sync: true);
 
   static const _EVENT_TYPE = 'KeyEvent';
 
   /**
    * An enumeration of key identifiers currently part of the W3C draft for DOM3
    * and their mappings to keyCodes.
    * http://www.w3.org/TR/DOM-Level-3-Events/keyset.html#KeySet-Set
    */
   static const Map<String, int> _keyIdentifier = const {
     'Up': KeyCode.UP,
@@ skipping 48 matching lines @@
    * KeyboardEvent controller.
    */
   _KeyboardEventHandler(this._type) :
     _target = null, super(_EVENT_TYPE) {
   }
 
   /**
    * Hook up all event listeners under the covers so we can estimate keycodes
    * and charcodes when they are not provided.
    */
-  _KeyboardEventHandler.initializeAllEventListeners(this._type, this._target) : 
+  _KeyboardEventHandler.initializeAllEventListeners(this._type, this._target) :
     super(_EVENT_TYPE) {
     Element.keyDownEvent.forTarget(_target, useCapture: true).listen(
         processKeyDown);
     Element.keyPressEvent.forTarget(_target, useCapture: true).listen(
         processKeyPress);
     Element.keyUpEvent.forTarget(_target, useCapture: true).listen(
         processKeyUp);
   }
 
   /**
@@ skipping 284 matching lines @@
       new _KeyboardEventHandler('keypress').forTarget(target);
 
   /** Named constructor to produce a stream for onKeyUp events. */
   static Stream<KeyEvent> onKeyUp(EventTarget target) =>
       new _KeyboardEventHandler('keyup').forTarget(target);
 
   /** Named constructor to produce a stream for onKeyDown events. */
   static Stream<KeyEvent> onKeyDown(EventTarget target) =>
     new _KeyboardEventHandler('keydown').forTarget(target);
 }