Remove now useless top level _wrap and _unwrap from dart:html.

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 {
   // TODO(podivilov): add type.
   final _ptr;
 
   final Map<String, EventListenerList> _listenerMap;
 
@@ skipping 33 matching lines @@
 
   EventListenerList remove(EventListener listener, [bool useCapture = false]) {
     _remove(listener, useCapture);
     return this;
   }
 
   bool dispatch(Event evt) {
     // TODO(jacobr): what is the correct behavior here. We could alternately
     // force the event to have the expected type.
     assert(evt.type == _type);
-    return _ptr.$dom_dispatchEvent(_unwrap(evt));
+    return _ptr.$dom_dispatchEvent(evt);
   }
 
   void _add(EventListener listener, bool useCapture) {
     _ptr.$dom_addEventListener(_type,
                           _findOrAddWrapper(listener, useCapture),
                           useCapture);
   }
 
   void _remove(EventListener listener, bool useCapture) {
     Function wrapper = _removeWrapper(listener, useCapture);
@@ skipping 25 matching lines @@
   Function _findOrAddWrapper(EventListener listener, bool useCapture) {
     if (_wrappers === null) {
       _wrappers = <_EventListenerWrapper>[];
     } else {
       for (_EventListenerWrapper wrapper in _wrappers) {
         if (wrapper.raw === listener && wrapper.useCapture == useCapture) {
           return wrapper.wrapped;
         }
       }
     }
-    final wrapped = (e) { listener(_wrap(e)); };
+    final wrapped = (e) { listener(e); };
     _wrappers.add(new _EventListenerWrapper(listener, wrapped, useCapture));
     return wrapped;
   }
 }
 
 class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 /*
 $!MEMBERS
 */
 }