anchor.diff:  import 'dart:io' hide FileSystemEntity;
   
   import 'package:args/args.dart';
  +import 'package:front_end/byte_store.dart';
   import 'package:front_end/file_system.dart' show FileSystemEntity;
   import 'package:front_end/front_end.dart';
  -import 'package:front_end/src/byte_store/protected_file_byte_store.dart';
   import 'package:front_end/incremental_kernel_generator.dart';
   import 'package:front_end/memory_file_system.dart';
   import 'package:front_end/physical_file_system.dart';
  +import 'package:front_end/src/byte_store/protected_file_byte_store.dart';
   import 'package:kernel/target/flutter.dart';
   import 'package:kernel/target/targets.dart';
   
  
positive.code: ArgParser argParser = new ArgParser()
    ..addOption('target',
        help: 'target platform', defaultsTo: 'vm', allowed: ['vm', 'flutter'])
    ..addOption('sdk-summary', help: 'Location of the sdk outline.dill file')
    ..addOption('sdk-library-specification',
        help: 'Location of the '
  
negative.code:       _fs.memory.entityForUri(uri).writeAsStringSync(contents);
  }
  
  ByteStore createByteStore(String cachePolicy, String path) {
    switch (cachePolicy) {
      case 'memory':
        return new MemoryByteStore();
      case 'protected':
        return new ProtectedFileByteStore(path);
      case 'evicting':
        return new MemoryCachingByteStore(
            new EvictingFileByteStore(path, 1024 * 1024 * 1024 /* 1G */),
            64 * 1024 * 1024 /* 64M */);
      default:
        throw new UnsupportedError('Unknown cache policy: $cachePolicy');
    }
  }
  
  /// A string replacement edit in a source file.
  class Edit {
    final Uri uri;
  