Make Zone API strong mode clean.

tools/dom/src/EventStreamProvider.dart

 // Copyright (c) 2013, 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;
 
 /**
  * A factory to expose DOM events as Streams.
  */
 class EventStreamProvider<T extends Event> {
@@ skipping 207 matching lines @@
 
 class _EventStreamSubscription<T extends Event> extends StreamSubscription<T> {
   int _pauseCount = 0;
   EventTarget _target;
   final String _eventType;
   EventListener _onData;
   final bool _useCapture;
 
   // TODO(leafp): It would be better to write this as
   // _onData = onData == null ? null :
-  //   onData is _wrapZoneCallback<Event, dynamic>
-  //     ? _wrapZone/*<Event, dynamic>*/(onData)
-  //     : _wrapZone/*<Event, dynamic>*/((e) => onData(e as T))
+  //   onData is void Function(Event)
+  //     ? _wrapZone<Event>(onData)
+  //     : _wrapZone<Event>((e) => onData(e as T))
   // In order to support existing tests which pass the wrong type of events but
   // use a more general listener, without causing as much slowdown for things
   // which are typed correctly.  But this currently runs afoul of restrictions
   // on is checks for compatibility with the VM.
   _EventStreamSubscription(
       this._target, this._eventType, void onData(T event), this._useCapture)
       : _onData = onData == null
             ? null
-            : _wrapZone<Event, dynamic>((e) => (onData as dynamic)(e)) {
+            : _wrapZone<Event>((e) => (onData as dynamic)(e)) {
     _tryResume();
   }
 
   Future cancel() {
     if (_canceled) return null;
 
     _unlisten();
     // Clear out the target to indicate this is complete.
     _target = null;
     _onData = null;
     return null;
   }
 
   bool get _canceled => _target == null;
 
   void onData(void handleData(T event)) {
     if (_canceled) {
       throw new StateError("Subscription has been canceled.");
     }
     // Remove current event listener.
     _unlisten();
-    _onData = _wrapZone/*<Event, dynamic>*/(handleData);
+    _onData = _wrapZone<Event>(handleData);
     _tryResume();
   }
 
   /// Has no effect.
   void onError(Function handleError) {}
 
   /// Has no effect.
   void onDone(void handleDone()) {}
 
   void pause([Future resumeSignal]) {
@@ skipping 166 matching lines @@
         e, _eventTypeGetter(e), useCapture);
   }
 
   String getEventType(EventTarget target) {
     return _eventTypeGetter(target);
   }
 
   String get _eventType =>
       throw new UnsupportedError('Access type through getEventType method.');
 }