Add constructors to all the event classes.

client/touch/Scrollbar.dart

 // Copyright (c) 2011, 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.
 
 /**
  * Implementation of a scrollbar for the custom scrolling behavior
  * defined in [:Scroller:].
  */
 class Scrollbar implements ScrollListener {
   /**
@@ skipping 202 matching lines @@
       }
       _scroller.setPosition(x, y);
     }
     _currentScrollStartMouse = coordinate;
   }
 
   void _onEnd(UIEvent e) {
     _scrollBarDragInProgress = false;
     // TODO(jacobr): make scrollbar less tightly coupled to the scroller.
     _scroller.onScrollerDragEnd.dispatch(
-        EventUtil.createEvent(ScrollerEventType.DRAG_END));
+        new Event(ScrollerEventType.DRAG_END));
   }
 
 
   /**
    * When scrolling ends, schedule a timeout to hide the scrollbars.
    */
   void _onScrollerEnd(Event e) {
     _cancelTimeout();
     _timerId = window.setTimeout(_boundHideFn, _DISPLAY_TIME);
     _scrollInProgress = false;
@@ skipping 107 matching lines @@
     style.setProperty(cssPos, '${pos}px', '');
     if (_cachedSize[cssSize] != size) {
       _cachedSize[cssSize] = size;
       style.setProperty(cssSize, '${size}px', '');
     }
     if (element.parent == null) {
       _frame.nodes.add(element);
     }
   }
 }