Revert "Zone support for Futures."

sdk/lib/async/event_loop.dart

 // Copyright (c) 2013, 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.async;
 
 typedef void _AsyncCallback();
 
 bool _callbacksAreEnqueued = false;
 Queue<_AsyncCallback> _asyncCallbacks = new Queue<_AsyncCallback>();
 
 void _asyncRunCallback() {
   // As long as we are iterating over the registered callbacks we don't
   // unset the [_callbacksAreEnqueued] boolean.
   while (!_asyncCallbacks.isEmpty) {
     Function callback = _asyncCallbacks.removeFirst();
     try {
       callback();
     } catch (e) {
       _AsyncRun._enqueueImmediate(_asyncRunCallback);
-      rethrow;
+      throw;
     }
   }
   // Any new callback must register a callback function now.
   _callbacksAreEnqueued = false;
 }
 
-void _scheduleAsyncCallback(callback) {
-  // Optimizing a group of Timer.run callbacks to be executed in the
-  // same Timer callback.
-  _asyncCallbacks.add(callback);
-  if (!_callbacksAreEnqueued) {
-    _AsyncRun._enqueueImmediate(_asyncRunCallback);
-    _callbacksAreEnqueued = true;
-  }
-}
-
 /**
  * Runs the given [callback] asynchronously.
  *
  * Callbacks registered through this function are always executed in order and
  * are guaranteed to run before other asynchronous events (like [Timer] events,
  * or DOM events).
  *
  * Warning: it is possible to starve the DOM by registering asynchronous
  * callbacks through this method. For example the following program will
  * run the callbacks without ever giving the Timer callback a chance to execute:
  *
  *     Timer.run(() { print("executed"); });  // Will never be executed;
  *     foo() {
  *       asyncRun(foo);  // Schedules [foo] in front of other events.
  *     }
  *     main() {
  *       foo();
  *     }
  */
 void runAsync(void callback()) {
-  _Zone._current.runAsync(callback);
+  // Optimizing a group of Timer.run callbacks to be executed in the
+  // same Timer callback.
+  _asyncCallbacks.add(callback);
+  if (!_callbacksAreEnqueued) {
+    _AsyncRun._enqueueImmediate(_asyncRunCallback);
+    _callbacksAreEnqueued = true;
+  }
 }
 
 class _AsyncRun {
   /** Enqueues the given callback before any other event in the event-loop. */
   external static void _enqueueImmediate(void callback());
 }