Retained size for instance in Observatory.

runtime/bin/vmservice/client/lib/src/elements/instance_view.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.
 
 library instance_view_element;
 
 import 'dart:async';
 import 'observatory_element.dart';
 import 'package:observatory/service.dart';
 import 'package:polymer/polymer.dart';
 
 @CustomTag('instance-view')
 class InstanceViewElement extends ObservatoryElement {
   @published ServiceMap instance;
 
   InstanceViewElement.created() : super.created();
 
   Future<ServiceObject> eval(String text) {
     return instance.isolate.get(
         instance.id + "/eval?expr=${Uri.encodeComponent(text)}");
   }
 
+  // TODO(koda): Add no-arg "calculate-link" instead of reusing "eval-link".
+  Future<ServiceObject> retainedSize(String dummy) {
+    return instance.isolate.get(instance.id + "/retained");
+  }
+
   void refresh(var done) {
     instance.reload().whenComplete(done);
   }
 }