anchor.diff:  import '../base/file_system.dart';
   import '../base/logger.dart';
   import '../base/process.dart';
  -import '../base/process_manager.dart';
   import '../base/utils.dart';
   import '../build_info.dart';
   import '../compile.dart';
  
positive.code:     return null;
    }
  
    final String genSnapshot = artifacts.getArtifactPath(Artifact.genSnapshot, platform, buildMode);
  
    final Directory outputDir = fs.directory(outputPath);
    outputDir.createSync(recursive: true);
    final String vmSnapshotData = fs.path.join(outputDir.path, 'vm_snapshot_data');
  
negative.code:     await outputDir.childFile('frontend_server.d')
          .writeAsString('frontend_server.d: ${artifacts.getArtifactPath(Artifact.frontendServerSnapshotForEngineDartSdk)}\n');
  
      genSnapshotArgs.addAll(<String>[
        '--reify-generic-functions',
        '--strong',
      ]);
    }
  
    genSnapshotArgs.add(mainPath);
  
    final int genSnapshotExitCode = await genSnapshot.run(
      snapshotType: new SnapshotType(platform, buildMode),
      packagesPath: packageMap.packagesPath,
      depfilePath: dependencies,
      additionalArgs: genSnapshotArgs,
    );
    if (genSnapshotExitCode != 0) {
      printError('Dart snapshot generator failed with exit code $genSnapshotExitCode');
      return null;
    }
  
  