Remove usage of dart:json.

sdk/lib/_internal/dartdoc/lib/src/client/client-live-nav.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.
 
 /** Provides client-side behavior for generated docs. */
 library client;
 
 import 'dart:html';
-import 'dart:json' as jsonlib;
+import 'dart:convert';
 // TODO(rnystrom): Use "package:" URL (#4968).
 import '../../classify.dart';
 import '../../markdown.dart' as md;
 import '../dartdoc/nav.dart';
 import 'dropdown.dart';
 import 'search.dart';
 import 'client-shared.dart';
 
 main() {
   setup();
 
   // Request the navigation data so we can build the HTML for it.
   HttpRequest.getString('${prefix}nav.json').then((text) {
-    var json = jsonlib.parse(text);
+    var json = JSON.decode(text);
     buildNavigation(json);
     setupSearch(json);
   });
 }
 
 
 /**
  * Takes [libraries], a JSON array representing a set of libraries and builds
  * the appropriate navigation DOM for it relative to the current library and
  * type.
@@ skipping 54 matching lines @@
     }
     html.write('</li>');
   }
 
   html.write('<ul class="icon">');
   types.forEach((typeInfo) =>
       writeType(kindToString(typeInfo[KIND]), typeInfo));
   exceptions.forEach((typeInfo) => writeType('exception', typeInfo));
   html.write('</ul>');
 }