pkg: analysis aided cleanup

pkg/scheduled_test/lib/src/schedule.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.
 
 library schedule;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:stack_trace/stack_trace.dart';
-import 'package:unittest/unittest.dart' as unittest;
 
 import 'mock_clock.dart' as mock_clock;
 import 'schedule_error.dart';
 import 'substitute_future.dart';
 import 'task.dart';
 import 'utils.dart';
-import 'value_future.dart';
 
 /// The schedule of tasks to run for a single test. This has three separate task
 /// queues: [tasks], [onComplete], and [onException]. It also provides
 /// visibility into the current state of the schedule.
 class Schedule {
   /// The main task queue for the schedule. These tasks are run before the other
   /// queues and generally constitute the main test body.
   TaskQueue get tasks => _tasks;
   TaskQueue _tasks;
 
@@ skipping 578 matching lines @@
   /// The string description of the callback.
   String get description {
     if (_description == null) _description = _thunk();
     return _description;
   }
 
   String toString() => description;
 
   PendingCallback._(this._thunk);
 }