Modernize the package's style.

lib/src/result_future.dart

-// Copyright (c) 2015, 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 async.result_future;
-
-import 'dart:async';
-
-import '../result.dart';
-import 'delegate/future.dart';
-
-/// A [Future] wrapper that provides synchronous access to the result of the
-/// wrapped [Future] once it's completed.
-class ResultFuture<T> extends DelegatingFuture<T> {
-  /// Whether the future has fired and [result] is available.
-  bool get isComplete => result != null;
-
-  /// The result of the wrapped [Future], if it's completed.
-  ///
-  /// If it hasn't completed yet, this will be `null`.
-  Result<T> get result => _result;
-  Result<T> _result;
-
-  factory ResultFuture(Future<T> future) {
-    var resultFuture;
-    resultFuture = new ResultFuture._(Result.capture(future).then((result) {
-      resultFuture._result = result;
-      return result.asFuture;
-    }));
-    return resultFuture;
-  }
-
-  ResultFuture._(Future<T> future)
-      : super(future);
-}