Make Completers asynchronous.

sdk/lib/async/future_impl.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.
 
 part of dart.async;
 
 deprecatedFutureValue(_FutureImpl future) =>
   future._isComplete ? future._resultOrListeners : null;
 
-class _CompleterImpl<T> implements Completer<T> {
+abstract class _Completer<T> implements Completer<T> {
   final Future<T> future;
   bool _isComplete = false;
 
-  _CompleterImpl() : future = new _FutureImpl<T>();
+  _Completer() : future = new _FutureImpl<T>();
+
+  void _setFutureValue(T value);
+  void _setFutureError(error);
 
   void complete([T value]) {
     if (_isComplete) throw new StateError("Future already completed");
     _isComplete = true;
-    _FutureImpl future = this.future;
-    future._setValue(value);
+    _setFutureValue(value);
   }
 
   void completeError(Object error, [Object stackTrace = null]) {
     if (_isComplete) throw new StateError("Future already completed");
     _isComplete = true;
     if (stackTrace != null) {
       // Force the stack trace onto the error, even if it already had one.
       _attachStackTrace(error, stackTrace);
     }
-    _FutureImpl future = this.future;
-    future._setError(error);
+    _setFutureError(error);
   }
 
   bool get isCompleted => _isComplete;
 }
 
+class _AsyncCompleter<T> extends _Completer<T> {
+  void _setFutureValue(T value) {
+    _FutureImpl future = this.future;
+    runAsync(() { future._setValue(value); });
+  }
+
+  void _setFutureError(error) {
+    _FutureImpl future = this.future;
+    runAsync(() { future._setError(error); });
+  }
+}
+
+class _SyncCompleter<T> extends _Completer<T> {
+  void _setFutureValue(T value) {
+    future._setValue(value);
+  }
+
+  void _setFutureError(error) {
+    future._setError(error);
+  }
+}
+
 /**
  * A listener on a future.
  *
  * When the future completes, the [_sendValue] or [_sendError] method
  * is invoked with the result.
  *
  * Listeners are kept in a linked list.
  */
 abstract class _FutureListener<T> {
   _FutureListener _nextListener;
@@ skipping 461 matching lines @@
   Future catchError(function(error), {bool test(var error)}) {
     return _future.catchError(function, test: test);
   }
 
   Future<T> whenComplete(action()) {
     return _future.whenComplete(action);
   }
 
   Stream<T> asStream() => new Stream.fromFuture(_future);
 }