pkg/docgen: fixed type references within typedef doc comments

pkg/docgen/lib/src/models/annotation.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.
 
 library docgen.models.annotation;
 
 import '../exports/mirrors_util.dart' as dart2js_util;
 import '../exports/source_mirrors.dart';
 
 import '../library_helpers.dart';
 
 import 'library.dart';
 import 'mirror_based.dart';
 
 /// Holds the name of the annotation, and its parameters.
-class Annotation extends MirrorBased {
+class Annotation extends MirrorBased<ClassMirror> {
   /// The class of this annotation.
   final ClassMirror mirror;
   final Library owningLibrary;
-  List<String> parameters;
+  final List<String> parameters;
 
   Annotation(InstanceMirror originalMirror, this.owningLibrary)
-      : mirror = originalMirror.type {
-    parameters = dart2js_util.variablesOf(originalMirror.type.declarations)
-        .where((e) => e.isFinal)
-        .map((e) => originalMirror.getField(e.simpleName).reflectee)
-        .where((e) => e != null)
-        .toList();
-  }
+      : mirror = originalMirror.type,
+        parameters = _createParamaters(originalMirror);
 
   Map toMap() => {
     'name': getDocgenObject(mirror, owningLibrary).docName,
     'parameters': parameters
   };
 }
+
+List<String> _createParamaters(InstanceMirror originalMirror) {
+  return dart2js_util.variablesOf(originalMirror.type.declarations)
+      .where((e) => e.isFinal)
+      .map((e) => originalMirror.getField(e.simpleName).reflectee)
+      .where((e) => e != null)
+      .toList();
+}