Add breadcrumb for the VM.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="view_footer.html">
 
 <polymer-element name="heap-map" extends="observatory-element">
 <template>
   <link rel="stylesheet" href="css/shared.css">
   <style>
     .hover {
       position: fixed;
       z-index: 999;
       height: 16px;
       width: 100%;
       background: #ffffff;
     }
     .spacer {
       height: 16px;
       background-color: red;
     }
   </style>
   <nav-bar pad="{{ false }}">
     <top-nav-menu></top-nav-menu>
+    <vm-nav-menu vm="{{ fragmentation.isolate.vm }}"></vm-nav-menu>
     <isolate-nav-menu isolate="{{ fragmentation.isolate }}"></isolate-nav-menu>
     <nav-menu link="{{ makeLink('/heap-map', fragmentation.isolate) }}" anchor="heap map" last="{{ true }}"></nav-menu>
     <nav-refresh callback="{{ refresh }}"></nav-refresh>
   </nav-bar>
   <div class="hover">
     <p style="text-align:center">{{ status }}</p>
   </div>
   <div class="spacer">
     <!-- Make sure no data is covered by hover bar initially -->
   </div>
   <div class="flex-row">
     <canvas id="fragmentation" width="1px" height="1px"></canvas>
   </div>
   <view-footer></view-footer>
 </template>
 </polymer-element>
 
 <script type="application/dart" src="heap_map.dart"></script>