Remove usage of dart:json.

utils/apidoc/mdn/prettyPrint.dart

 /**
  * Creates database.html, examples.html, and obsolete.html.
  */
 
 library prettyPrint;
 
+import 'dart:convert';
 import 'dart:io';
-import 'dart:json' as json;
 import 'util.dart';
 
 String orEmpty(String str) {
   return str == null ? "" : str;
 }
 
 List<String> sortStringCollection(Iterable<String> collection) {
   final out = <String>[];
   out.addAll(collection);
   out.sort((String a, String b) => a.compareTo(b));
@@ skipping 25 matching lines @@
   }
 
   addMissingHelper('properties');
   addMissingHelper('methods');
   addMissingHelper('constants');
   return total;
 }
 
 void main() {
   // Database of code documentation.
-  final Map<String, Map> database = json.parse(
+  final Map<String, Map> database = JSON.decode(
       new File('output/database.filtered.json').readAsStringSync());
 
   // Types we have documentation for.
   matchedTypes = new Set<String>();
   int numMissingMethods = 0;
   int numFoundMethods = 0;
   int numExtraMethods = 0;
   int numGen = 0;
   int numSkipped = 0;
   final sbSkipped = new StringBuffer();
@@ skipping 356 matching lines @@
           <th>IDL</th>
           <th>Status</th>
         </tr>
 $sbObsolete
     </tbody>
    </table>
   </body>
  </html>
  """);
 }