Fix a bug: observatory debugger can't expand instances.

runtime/observatory/lib/src/elements/debugger.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 debugger_page_element;
 
 import 'dart:async';
 import 'dart:svg';
 import 'dart:html';
 import 'dart:math';
@@ skipping 1951 matching lines @@
 
   factory DebuggerPageElement(S.Isolate isolate, M.InstanceRepository instances,
       M.ScriptRepository scripts, M.EventRepository events) {
     assert(isolate != null);
     assert(instances != null);
     assert(scripts != null);
     assert(events != null);
     final e = document.createElement(tag.name);
     final debugger = new ObservatoryDebugger(isolate);
     debugger.page = e;
+    debugger.instances = instances;
     e._isolate = isolate;
     e._debugger = debugger;
     e._instances = instances;
     e._scripts = scripts;
     e._events = events;
     return e;
   }
 
   DebuggerPageElement.created() : super.created();
 
@@ skipping 1274 matching lines @@
   ..setAttribute('height', '24')
   ..children = [
     new PathElement()
       ..setAttribute(
           'd',
           'M11 17h2v-6h-2v6zm1-15C6.48 2 2 6.48 2 12s4.48 10 '
           '10 10 10-4.48 10-10S17.52 2 12 2zm0 18c-4.41 '
           '0-8-3.59-8-8s3.59-8 8-8 8 3.59 8 8-3.59 8-8 8zM11 '
           '9h2V7h-2v2z')
   ];