Events operator [] shouldn't convert event name to lower case.

lib/dom/templates/html/dartium/impl_EventTarget.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.
 
 class _EventsImpl implements Events {
 
   final _EventTargetImpl _ptr;
 
   final Map<String, EventListenerList> _listenerMap;
 
   _EventsImpl(this._ptr) : _listenerMap = <EventListenerList>{};
 
   EventListenerList operator [](String type) {
-    return _get(type.toLowerCase());
-  }
-  
-  EventListenerList _get(String type) {
     return _listenerMap.putIfAbsent(type,
       () => new _EventListenerListImpl(_ptr, type));
   }
 }
 
 class _EventListenerWrapper {
   final EventListener raw;
   final Function wrapped;
   final bool useCapture;
   _EventListenerWrapper(this.raw, this.wrapped, this.useCapture);
@@ skipping 78 matching lines @@
 
   Events _on;
 
   Events get on() {
     if (_on == null) _on = new _EventsImpl(this);
     return _on;
   }
 
 $!MEMBERS
 }