Fixed toMap() for subclasses

pkg/docgen/lib/docgen.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.
 
 /**
  * **docgen** is a tool for creating machine readable representations of Dart
  * code metadata, including: classes, members, comments and annotations.
  *
  * docgen is run on a `.dart` file or a directory containing `.dart` files.
  *
@@ skipping 653 matching lines @@
   }
   
   /// Generates a map describing the [Class] object.
   Map toMap() => {
     'name': name,
     'qualifiedname': qualifiedName,
     'comment': comment,
     'superclass': validSuperclass(),
     'implements': interfaces.where(_isVisible)
         .map((e) => e.qualifiedName).toList(),
-    'subclass': subclasses,
+    'subclass': subclasses.toList(),
     'variables': recurseMap(variables),
     'inheritedvariables': recurseMap(inheritedVariables),
     'methods': methods.toMap(),
     'inheritedmethods': inheritedMethods.toMap(),
     'annotations': annotations.map((a) => a.toMap()).toList(),
     'generics': recurseMap(generics)
   };
 }
 
 /**
@@ skipping 334 matching lines @@
   String qualifiedName;
   List<String> parameters; 
   
   Annotation(this.qualifiedName, this.parameters);
   
   Map toMap() => {
     'name': qualifiedName,
     'parameters': parameters
   };
 }