Revert "Switch libraries to using new tags."

sdk/lib/isolate/timer.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.
 
-part of dart_isolate;
-
 abstract class Timer {
   /**
    * Creates a new timer. The [callback] callback is invoked after
    * [milliSeconds] milliseconds.
    */
   factory Timer(int milliSeconds, void callback(Timer timer)) {
     if (_TimerFactory._factory == null) {
       throw new UnsupportedError("Timer interface not supported.");
     }
     return _TimerFactory._factory(milliSeconds, callback, false);
@@ skipping 25 matching lines @@
 
 class _TimerFactory {
   static _TimerFactoryClosure _factory;
 }
 
 // TODO(ahe): Warning: this is NOT called by Dartium. Instead, it sets
 // [_TimerFactory._factory] directly.
 void _setTimerFactoryClosure(_TimerFactoryClosure closure) {
   _TimerFactory._factory = closure;
 }