-Fix display of megamorphic miss function.

runtime/observatory/lib/src/elements/inbound_reference.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 inbound_reference_element;
 
 import 'dart:async';
 import 'package:polymer/polymer.dart';
 import 'package:observatory/service.dart';
 import 'observatory_element.dart';
 
 @CustomTag('inbound-reference')
 class InboundReferenceElement extends ObservatoryElement {
   @published ObservableMap ref;
   InboundReferenceElement.created() : super.created();
 
-  ServiceObject get source => ref['source'];
-
   // I.e., inbound references to 'source' for recursive pointer chasing.
   @observable ObservableList inboundReferences;
   Future<ServiceObject> fetchInboundReferences(arg) {
+    var source = ref['source'];
     return source.isolate.getInboundReferences(source, arg)
         .then((ServiceMap response) {
           inboundReferences = new ObservableList.from(response['references']);
         });
   }
 
   // TODO(turnidge): This is here to workaround vm/dart2js differences.
   dynamic expander() {
     return expandEvent;
   }
 
   void expandEvent(bool expand, Function onDone) {
     if (expand) {
       fetchInboundReferences(100).then((result) {
         notifyPropertyChange(#ref, 0, 1);
       }).whenComplete(onDone);
     } else {
       inboundReferences = null;
       onDone();
     }
   }
 }