anchor.diff:    Uri myLocation =
         handler.provider.cwd.resolveUri(Platform.script);
   
  +  List<Uri> uris = <Uri>[];
  +
  +  if (arguments.length > 1) {
  +    // Compute tags for libraries requested by the user.
  +    uris.addAll(
  +        arguments.skip(1).map((argument) => Uri.base.resolve(argument)));
  +  } else {
  +    // Compute tags for dart2js itself.
  +    uris.add(myLocation.resolve(DART2JS));
  +    uris.add(myLocation.resolve(DART2JS_MIRROR));
  +  }
  +
     // Get the names of public dart2js libraries.
     Iterable<String> names = LIBRARIES.keys.where(isPublicDart2jsLibrary);
   
     // Prepend "dart:" to the names.
  -  List<Uri> uris = names.map((String name) => Uri.parse('dart:$name')).toList();
  -
  -  // Append dart2js itself.
  -  uris.add(myLocation.resolve(DART2JS));
  -  uris.add(myLocation.resolve(DART2JS_MIRROR));
  +  uris.addAll(names.map((String name) => Uri.parse('dart:$name')));
   
     Uri libraryRoot = myLocation.resolve(SDK_ROOT);
     Uri packageRoot = Uri.base.resolve(Platform.packageRoot);
  
positive.code: //       # Replace "xcodebuild" with "out" on Linux, and "build" on Windows.
  //       "-pdart/xcodebuild/ReleaseIA32/packages/",
  //       "dart/pkg/compiler/samples/darttags/darttags.dart",
  //       "dart/TAGS"
  //     ],
  //   },
  // ]
  
negative.code: import 'package:compiler/src/source_file_provider.dart';
  import 'package:compiler/src/util/uri_extras.dart';
  
  const DART2JS = 'package:compiler/src/dart2js.dart';
  const DART2JS_MIRROR = 'package:compiler/src/mirrors/dart2js_mirrors.dart';
  const SDK_ROOT = '../../../../sdk/';
  
  bool isPublicDart2jsLibrary(String name) {
  