Remove usage of dart:json.

sdk/lib/_internal/dartdoc/lib/dartdoc.dart

 // Copyright (c) 2013, 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.
 
 /**
  * To generate docs for a library, run this script with the path to an
  * entrypoint .dart file, like:
  *
  *     $ dart dartdoc.dart foo.dart
  *
  * This will create a "docs" directory with the docs for your libraries. To
  * create these beautiful docs, dartdoc parses your library and every library
  * it imports (recursively). From each library, it parses all classes and
  * members, finds the associated doc comments and builds crosslinked docs from
  * them.
  */
 library dartdoc;
 
 import 'dart:async';
+import 'dart:convert';
 import 'dart:io';
 import 'dart:isolate';
-import 'dart:json' as json;
 import 'dart:math';
 
 import 'package:path/path.dart' as path;
 
 import 'classify.dart';
 import 'markdown.dart' as md;
 import 'universe_serializer.dart';
 
 import 'src/dartdoc/nav.dart';
 import 'src/dartdoc/utils.dart';
@@ skipping 738 matching lines @@
   void docIndexLibrary(LibraryMirror library) {
     writeln('<h4>${a(libraryUrl(library), displayName(library))}</h4>');
   }
 
   /**
    * Walks the libraries and creates a JSON object containing the data needed
    * to generate navigation for them.
    */
   void docNavigationJson() {
     startFile('nav.json');
-    writeln(json.stringify(createNavigationInfo()));
+    writeln(JSON.encode(createNavigationInfo()));
     endFile();
   }
   /// Whether dartdoc is running from within the Dart SDK or the
   /// Dart source repository.
   bool get runningFromSdk =>
     path.extension(Platform.script) == '.snapshot';
 
   /// Gets the path to the root directory of the SDK.
   String get sdkDir =>
     path.dirname(path.dirname(Platform.executable));
 
   /// Gets the path to the dartdoc directory normalized for running in different
   /// places.
   String get normalizedDartdocPath => path.normalize(
       path.absolute(runningFromSdk ?
           path.join(sdkDir, 'lib', '_internal', 'dartdoc') :
           dartdocPath.toString()));
 
   void docNavigationDart() {
     var tmpDir = new Directory(tmpPath);
     if (!tmpDir.existsSync()) {
         tmpDir.createSync();
     }
-    String jsonString = json.stringify(createNavigationInfo());
+    String jsonString = JSON.encode(createNavigationInfo());
     String dartString = jsonString.replaceAll(r"$", r"\$");
     var filePath = path.join(tmpPath, 'client.dart');
 
     var clientDir = path.join(normalizedDartdocPath,'lib', 'src', 'client');
 
     writeString(new File(filePath),
         '''library client;
         import 'dart:html';
         import 'dart:json';
         import r'${path.toUri(path.join(clientDir, 'client-shared.dart'))}';
@@ skipping 1504 matching lines @@
    return '''
         <div class="mdn">
         $mdnComment
         <div class="mdn-note"><a href="$mdnUrl">from MDN</a></div>
         </div>
         ''';
   }
 
   String toString() => mdnComment;
 }