Rename runAsync to scheduleMicrotask.

tests/lib/async/zone_run_unary_test.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.
 
 import 'package:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'dart:async';
 
 main() {
   Completer done = new Completer();
@@ skipping 26 matching lines @@
     Expect.fail("should not be invoked");
   }, 99);
   Expect.equals(42, result);
   events.add("executed run2");
 
   asyncStart();
   shouldForward = true;
   result = forked.runUnary((arg) {
     Expect.identical(forked, Zone.current);
     events.add("run closure 2");
-    runAsync(() {
+    scheduleMicrotask(() {
       events.add("run closure 3");
       Expect.identical(forked, Zone.current);
       done.complete(true);
     });
     return -arg - 8;
   }, 490);
-  events.add("after nested runAsync");
+  events.add("after nested scheduleMicrotask");
   Expect.equals(-499, result);
 
   done.future.whenComplete(() {
     Expect.listEquals(
         ["zone forked", "forked.run1", "run closure", "executed run",
          "forked.run1", "executed run2", "forked.run1", "run closure 2",
-          "after nested runAsync", "run closure 3"],
+          "after nested scheduleMicrotask", "run closure 3"],
         events);
     asyncEnd();
   });
 }