anchor.diff:  import '../base/process.dart';
   import '../base/utils.dart';
   import '../build_info.dart';
  -import '../dart/sdk.dart';
  +import '../dart/package_map.dart';
   import '../globals.dart';
   import '../run.dart';
   import '../runner/flutter_command.dart';
  
positive.code:     genSnapshot,
      '--vm_isolate_snapshot=$vmIsolateSnapshot',
      '--isolate_snapshot=$isolateSnapshot',
      '--package_root=$packagesPath',
      '--url_mapping=dart:mojo.internal,$mojoInternalPath',
      '--url_mapping=dart:ui,$uiPath',
      '--url_mapping=dart:jni,$jniPath',
  
negative.code:   }
  }
  
  String _getSdkExtensionPath(PackageMap packageMap, String package) {
    return path.dirname(packageMap.map[package].toFilePath());
  }
  
  /// Build an AOT snapshot. Return `null` (and log to `printError`) if the method
  