Add breadcrumb for the VM.

runtime/observatory/lib/src/elements/context_view.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="object_common.html">
 <link rel="import" href="context_ref.html">
 <link rel="import" href="view_footer.html">
 
 <polymer-element name="context-view" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
       <top-nav-menu></top-nav-menu>
+      <vm-nav-menu vm="{{ context.isolate.vm }}"></vm-nav-menu>
       <isolate-nav-menu isolate="{{ context.isolate }}"></isolate-nav-menu>
       <!-- TODO(turnidge): Add library nav menu here. -->
       <class-nav-menu cls="{{ context.clazz }}"></class-nav-menu>
       <nav-menu link="." anchor="instance" last="{{ true }}"></nav-menu>
       <nav-refresh callback="{{ refresh }}"></nav-refresh>
     </nav-bar>
 
     <template if="{{ !context.isError }}">
       <div class="content">
         <h1>instance of Context</h1>
@@ skipping 30 matching lines @@
             </div>
           </curly-block><br><br>
         </template>
       </div>
     </template>
     <view-footer></view-footer>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="context_view.dart"></script>