Convert shelf to use the string_scanner package.

pkg/shelf/test/harness_console.dart

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 /*
  * This file imports all individual tests files and allows them to be run
  * all at once.
  *
  * It also exposes `testCore` which is used by `hop_runner` to rust tests via
  * Hop.
  */
 library harness_console;
 
 import 'package:unittest/unittest.dart';
 
 import 'create_middleware_test.dart' as create_middleware;
 import 'http_date_test.dart' as http_date;
 import 'log_middleware_test.dart' as log_middleware;
 import 'media_type_test.dart' as media_type;
 import 'request_test.dart' as request;
 import 'response_test.dart' as response;
 import 'shelf_io_test.dart' as shelf_io;
 import 'stack_test.dart' as stack;
-import 'string_scanner_test.dart' as string_scanner;
 
 void main() {
   groupSep = ' - ';
 
   group('createMiddleware', create_middleware.main);
   group('http_date', http_date.main);
   group('logRequests', log_middleware.main);
   group('MediaType', media_type.main);
   group('Request', request.main);
   group('Response', response.main);
   group('shelf_io', shelf_io.main);
   group('Stack', stack.main);
-  group('StringScanner', string_scanner.main);
 }