Allow matchingTarget to also include the currentTarget.

tools/dom/templates/html/impl/impl_Event.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.
 
 // WARNING: Do not edit - generated code.
 
 part of $LIBRARYNAME;
 
 $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
   // In JS, canBubble and cancelable are technically required parameters to
@@ skipping 32 matching lines @@
    * accessing this value will throw an [UnsupportedError].
    */
   Element get matchingTarget {
     if (_selector == null) {
       throw new UnsupportedError('Cannot call matchingTarget if this Event did'
           ' not arise as a result of event delegation.');
     }
     var currentTarget = this.currentTarget;
     var target = this.target;
     var matchedTarget;
-    while (matchedTarget == null && target != currentTarget && target != null) {
-      if (target.matches(_selector)) {
-        matchedTarget = target;
-      }
+    do {
+      if (target.matches(_selector)) return target;
       target = target.parent;
-    }
-    return matchedTarget;
+    } while (target != null && target != currentTarget.parent);
+    throw new StateError('No selector matched for populating matchedTarget.');
   }
 $!MEMBERS
 }