Generate useful toString() methods for summary classes.

pkg/analyzer/lib/src/summary/base.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.
 
 /**
  * Base functionality which code generated summary classes are built upon.
  */
 library analyzer.src.summary.base;
 
 /**
@@ skipping 15 matching lines @@
  * Instances of this class represent data that has been read from a summary.
  */
 abstract class SummaryClass {
   /**
    * Translate the data in this class into a map whose keys are the names of
    * fields and whose values are the data stored in those fields.
    *
    * Intended for testing and debugging only.
    */
   Map<String, Object> toMap();
+
+  /**
+   * Translate the data in this class into a JSON map, whose keys are the names
+   * of fields and whose values are the data stored in those fields,
+   * recursively converted into JSON.
+   *
+   * Fields containing their default value are elided.
+   *
+   * Intended for testing and debugging only.
+   */
+  Map<String, Object> toJson();
 }