Revert "Zone support for Futures."

sdk/lib/async/event_loop.dart

Index: sdk/lib/async/event_loop.dart
diff --git a/sdk/lib/async/event_loop.dart b/sdk/lib/async/event_loop.dart
index bc0a63818b90aa0164a12d0039be8d377b2f270f..2802e40d55ec75e41a0426a65abe5babd6b642c1 100644
--- a/sdk/lib/async/event_loop.dart
+++ b/sdk/lib/async/event_loop.dart
@@ -18,23 +18,13 @@ void _asyncRunCallback() {
       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.
  *
@@ -55,7 +45,13 @@ void _scheduleAsyncCallback(callback) {
  *     }
  */
 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 {