Revert "Removing setImmediate and hiding WindowTimers interface"

samples/clock/web/clock.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.
 
 library clock;
 
-import 'dart:async';
 import 'dart:html';
 import 'dart:math';
 
 part 'balls.dart';
 part 'numbers.dart';
 
 void main() {
   new CountDownClock();
 }
 
@@ skipping 138 matching lines @@
 
 void setElementPosition(Element elem, double x, double y) {
   elem.style.transform = 'translate(${x}px, ${y}px)';
 }
 
 void setElementSize(Element elem, double l, double t, double r, double b) {
   setElementPosition(elem, l, t);
   elem.style.right = "${r}px";
   elem.style.bottom = "${b}px";
 }