anchor.diff:        _evictionIsolateIsRunning = true;
         try {
           ReceivePort response = new ReceivePort();
  -        _cleanUpSendPort.send(new _CacheCleanUpRequest(
  +        _cleanUpSendPort.send(new CacheCleanUpRequest(
               _cachePath, _maxSizeBytes, response.sendPort));
           await response.first;
         } finally {
  
positive.code:     return new File(join(_cachePath, key));
    }
  }
  
  /**
   * The request that is sent from the main isolate to the clean-up isolate.
   */
  class _CacheCleanUpRequest {
    final String cachePath;
    final int maxSizeBytes;
    final SendPort replyTo;
  
    _CacheCleanUpRequest(this.cachePath, this.maxSizeBytes, this.replyTo);
  }
  
negative.code: 
  import 'package:analyzer/src/dart/analysis/byte_store.dart';
  import 'package:path/path.dart';
  
  /**
   * The request that is sent from the main isolate to the clean-up isolate.
   */
  class CacheCleanUpRequest {
    final String cachePath;
    final int maxSizeBytes;
    final SendPort replyTo;
  
    CacheCleanUpRequest(this.cachePath, this.maxSizeBytes, this.replyTo);
  }
  
  /**
   * [ByteStore] that stores values as files and performs cache eviction.
  