anchor.diff:      Compiler newCompiler,
       LibraryUpdater updater,
       int position) {
  +
     cachedCompiler = newCompiler;
  +  if (poiTask == null || poiTask.compiler != cachedCompiler) {
  +    poiTask = new PoiTask(cachedCompiler);
  +    cachedCompiler.tasks.add(poiTask);
  +  }
   
     Future<bool> compilation = cachedCompiler.run(updater.uri);
   
  
positive.code:   LibraryUpdater updater =
        new LibraryUpdater(
            cachedCompiler, inputProvider, script, printWallClock, printVerbose);
  
    return reuseCompiler(
        diagnosticHandler: handler,
  
negative.code: 
  import 'package:compiler/implementation/dart2jslib.dart' show
      Compiler,
      CompilerTask,
      Enqueuer,
      QueueFilter,
      WorkItem;
  