Remove support for attribute event listeners.

client/samples/spirodraw/ColorPicker.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.
 
 typedef void PickerListener(String selectedColor);
 
 class ColorPicker {
 
   static final hexValues = const ['00', '33', '66', '99', 'CC', 'FF'];
   static final COLS = 18;
@@ skipping 46 matching lines @@
   }
 
   /**
    * Adds a [PickerListener] to receive updates.
    */
   void addListener(PickerListener listener) {
     _listeners.add(listener);
   }
 
   void addHandlers() {
-    canvasElement.onmousemove = (e) { onMouseMove(e); };
-    canvasElement.onmousedown = (e) { onMouseDown(e); };
+    canvasElement.addEventListener('mousemove', (e) => onMouseMove(e), true);
+    canvasElement.addEventListener('mousedown', (e) => onMouseDown(e), true);
   }
 
    void drawPalette() {
     int i=0;
     for (int r=0; r < 256; r+=51) {
       for (int g=0; g < 256; g+=51) {
         for (int b=0; b < 256; b+=51) {
           String color = getHexString(i);
           ctx.fillStyle = color;
           int x = BW * (i % COLS);
@@ skipping 25 matching lines @@
   }
   
   String getHexString(int i) {
     int r = i ~/ 36;
     int g = (i % 36) ~/ 6;
     int b = i % 6;
     return '#${hexValues[r]}${hexValues[g]}${hexValues[b]}';
   }
   
 }