anchor.diff:      // Compute files referencing a name.
       if (_referencingNameTasks.isNotEmpty) {
         _FilesReferencingNameTask task = _referencingNameTasks.first;
  -      bool isDone = await task.perform();
  +      bool isDone = task.perform();
         if (isDone) {
           _referencingNameTasks.remove(task);
         }
  
positive.code:     if (_definingClassMemberNameTasks.isNotEmpty) {
        _FilesDefiningClassMemberNameTask task =
            _definingClassMemberNameTasks.first;
        bool isDone = await task.perform();
        if (isDone) {
          _definingClassMemberNameTasks.remove(task);
        }
  
negative.code:    * scenarios. Instead we use a fixed length of time, so we can spend less time
     * overall and keep quick enough response time.
     */
    bool perform() {
      Stopwatch timer = new Stopwatch()..start();
      while (timer.elapsedMilliseconds < _MS_WORK_INTERVAL) {
        // Prepare files to check.
  