anchor.diff:        new IOPipeline([
           SourceToDillStep(),
           GlobalAnalysisStep(),
  -        Dart2jsBackendStep(),
  +        Dart2jsCodegenStep(codeId0),
  +        Dart2jsCodegenStep(codeId1),
  +        Dart2jsEmissionStep(),
           RunD8(),
         ], cacheSharedModules: true));
   }
  
positive.code:   }
  }
  
  // Step that invokes the dart2js backend on the main module given the results of
  // the global analysis step.
  class Dart2jsBackendStep implements IOModularStep {
    @override
    List<DataId> get resultData => const [jsId];
  
    @override
    bool get needsSources => false;
  
negative.code: /// This is a shell that runs multiple tests, one per folder under `data/`.
  import 'dart:io';
  
  import 'package:compiler/src/commandline_options.dart';
  import 'package:expect/expect.dart';
  import 'package:front_end/src/compute_platform_binaries_location.dart'
      show computePlatformBinariesLocation;
  