anchor.diff:  const String _kSnapshotKey = 'snapshot_blob.bin';
   const String _kDylibKey = 'libapp.so';
   
  -Future<int> createSnapshot({
  +Future<int> _createSnapshot({
     @required String mainPath,
     @required String snapshotPath,
  -  String depfilePath,
  +  @required String depfilePath,
     @required String packages
   }) {
     assert(mainPath != null);
     assert(snapshotPath != null);
  +  assert(depfilePath != null);
     assert(packages != null);
     final String snapshotterPath = artifacts.getArtifactPath(Artifact.genSnapshot, null, BuildMode.debug);
     final String vmSnapshotData = artifacts.getArtifactPath(Artifact.vmSnapshotData);
  
positive.code: 
      // In a precompiled snapshot, the instruction buffer contains script
      // content equivalents
      final int result = await createSnapshot(
        mainPath: mainPath,
        snapshotPath: snapshotPath,
        depfilePath: depfilePath,
  
negative.code:     '--vm_snapshot_data=$vmSnapshotData',
      '--isolate_snapshot_data=$isolateSnapshotData',
      '--packages=$packages',
      '--script_snapshot=$snapshotPath',
      '--dependencies=$depfilePath',
      mainPath,
    ];
    fs.file(depfilePath).parent.childFile('gen_snapshot.d').writeAsString('$depfilePath: $snapshotterPath\n');
    return runCommandAndStreamOutput(args);
  }
  
  