Move json to lib/json/{json.dart, json_frog.dart}

frog/leg/scanner/source_list.dart

 // Copyright (c) 2012, 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.
 
 final List<String> argv = const <String>[
 '../client/base/AnimationScheduler.dart',
 '../client/base/Device.dart',
 '../client/base/DomWrapper.dart',
 '../client/base/Env.dart',
 '../client/base/base.dart',
@@ skipping 1194 matching lines @@
 '../client/html/src/WorkerWrappingImplementation.dart',
 '../client/html/src/XMLHttpRequest.dart',
 '../client/html/src/XMLHttpRequestProgressEvent.dart',
 '../client/html/src/XMLHttpRequestProgressEventWrappingImplementation.dart',
 '../client/html/src/XMLHttpRequestUpload.dart',
 '../client/html/src/XMLHttpRequestUploadWrappingImplementation.dart',
 '../client/html/src/XMLHttpRequestWrappingImplementation.dart',
 '../client/html/src/_Collections.dart',
 '../client/html/src/_FactoryProviders.dart',
 '../client/html/src/_ListIterators.dart',
-'../client/json/dart_json.dart',
-'../client/json/json.dart',
+'../lib/json/json.dart',
+'../lib/json/json_dart.dart',
 '../client/layout/GridLayout.dart',
 '../client/layout/GridLayoutParams.dart',
 '../client/layout/GridLayoutParser.dart',
 '../client/layout/GridTracks.dart',
 '../client/layout/SizingFunctions.dart',
 '../client/layout/ViewLayout.dart',
 '../client/layout/layout.dart',
 '../client/observable/ChangeEvent.dart',
 '../client/observable/EventBatch.dart',
 '../client/observable/observable.dart',
@@ skipping 230 matching lines @@
 './tokenizer.dart',
 './tokenizer.g.dart',
 './tree.dart',
 './tree.g.dart',
 './type.dart',
 './utils.dart',
 './value.dart',
 './var_member.dart',
 './world.dart',
 'leg/scanner/file_with_non_ascii.dart' ];