Refactor Future constructors.

sdk/lib/_internal/compiler/implementation/lib/isolate_helper.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.
 
 library _isolate_helper;
 
 import 'dart:async';
 import 'dart:collection' show Queue, HashMap;
 import 'dart:isolate';
 import 'dart:_js_helper' show convertDartClosureToJS,
@@ skipping 817 matching lines @@
   /** Internal counter to assign unique ids to each port. */
   static int _idCount = 0;
 
   /** For implementing equals and hashcode. */
   final int _id;
 
   /** Underlying port, when resolved. */
   SendPort _port;
 
   /**
-   * Future of the underlying port, so that we can detect when this port can be
+   * Future.sync the underlying port, so that we can detect when this port can be
    * sent on messages.
    */
   Future<SendPort> _futurePort;
 
   /** Pending messages (and reply ports). */
   List pending;
 
   _BufferingSendPort(isolateId, this._futurePort)
       : super(isolateId), _id = _idCount, pending = [] {
     _idCount++;
@@ skipping 577 matching lines @@
         JS('void', '#.clearInterval(#)', globalThis, _handle);
       }
       _handle = null;
     } else {
       throw new UnsupportedError("Canceling a timer.");
     }
   }
 }
 
 bool hasTimer() => JS('', '#.setTimeout', globalThis) != null;