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

lib/dom/templates/html/dartium/impl_EventTarget.darttemplate

Index: lib/dom/templates/html/dartium/impl_EventTarget.darttemplate
diff --git a/lib/dom/templates/html/dartium/impl_EventTarget.darttemplate b/lib/dom/templates/html/dartium/impl_EventTarget.darttemplate
index 8eb8ed7022ecf01b97a30a77cde3d6e04fee1dd2..9ad91e163da3d1d3fbf020f051c7d6f9734f1760 100644
--- a/lib/dom/templates/html/dartium/impl_EventTarget.darttemplate
+++ b/lib/dom/templates/html/dartium/impl_EventTarget.darttemplate
@@ -51,7 +51,7 @@ class _EventListenerListImpl implements EventListenerList {
     // 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) {
@@ -97,7 +97,7 @@ class _EventListenerListImpl implements EventListenerList {
         }
       }
     }
-    final wrapped = (e) { listener(_wrap(e)); };
+    final wrapped = (e) { listener(e); };
     _wrappers.add(new _EventListenerWrapper(listener, wrapped, useCapture));
     return wrapped;
   }