Reapply "Zone support for Futures, Timer, Streams."

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 2802e40d55ec75e41a0426a65abe5babd6b642c1..bc0a63818b90aa0164a12d0039be8d377b2f270f 100644
--- a/sdk/lib/async/event_loop.dart
+++ b/sdk/lib/async/event_loop.dart
@@ -18,13 +18,23 @@ void _asyncRunCallback() {
       callback();
     } catch (e) {
       _AsyncRun._enqueueImmediate(_asyncRunCallback);
-      throw;
+      rethrow;
     }
   }
   // 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.
  *
@@ -45,13 +55,7 @@ void _asyncRunCallback() {
  *     }
  */
 void runAsync(void 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;
-  }
+  _Zone._current.runAsync(callback);
 }
 
 class _AsyncRun {