Refactor the event-generation code to locate it in systemhtml.py.

client/html/generated/html/frog/Element.dart

 // 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.
 
 // TODO(jacobr): use _Lists.dart to remove some of the duplicated
 // functionality.
 class _ChildrenElementList implements ElementList {
   // Raw Element.
   final _ElementImpl _element;
   final _HTMLCollectionImpl _childElements;
@@ skipping 520 matching lines @@
      // TODO(jacobr): last param should be null, see b/5045788
      return getComputedStyle('');
   }
 
   Future<CSSStyleDeclaration> getComputedStyle(String pseudoElement) {
     return _createMeasurementFuture(() =>
             window._getComputedStyle(this, pseudoElement),
         new Completer<CSSStyleDeclaration>());
   }
 
+  _ElementEventsImpl get on() =>
+    new _ElementEventsImpl(this);
+
   static final int ALLOW_KEYBOARD_INPUT = 1;
 
   int get _childElementCount() native "return this.childElementCount;";
 
   _HTMLCollectionImpl get _children() native "return this.children;";
 
   final _DOMTokenListImpl classList;
 
   String get _className() native "return this.className;";
 
@@ skipping 64 matching lines @@
   final String tagName;
 
   String title;
 
   bool translate;
 
   final String webkitRegionOverflow;
 
   String webkitdropzone;
 
-  _ElementEventsImpl get on() =>
-    new _ElementEventsImpl(this);
-
   void blur() native;
 
   void click() native;
 
   void focus() native;
 
   String _getAttribute(String name) native "return this.getAttribute(name);";
 
   _ClientRectImpl _getBoundingClientRect() native "return this.getBoundingClientRect();";
 
@@ skipping 117 matching lines @@
   EventListenerList get touchEnd() => _get('touchend');
 
   EventListenerList get touchLeave() => _get('touchleave');
 
   EventListenerList get touchMove() => _get('touchmove');
 
   EventListenerList get touchStart() => _get('touchstart');
 
   EventListenerList get transitionEnd() => _get('webkitTransitionEnd');
 }