Add breadcrumb for the VM.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
 
 <polymer-element name="metrics-page" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
       ul li:hover:not(.selected) {
         background-color: #FFF3E3;
       }
       .selected {
         background-color: #0489c3;
       }
       .graph {
         min-height: 600px;
       }
     </style>
     <nav-bar>
-      <top-nav-menu last="{{ true }}"></top-nav-menu>
+      <top-nav-menu></top-nav-menu>
+      <vm-nav-menu vm="{{ isolate.vm }}"></vm-nav-menu>
+      <isolate-nav-menu isolate="{{ isolate }}"></isolate-nav-menu>
+      <nav-menu link="{{ makeLink('/metrics', isolate) }}" anchor="metrics" last="{{ true }}"></nav-menu>
+
       <nav-refresh callback="{{ refresh }}"></nav-refresh>
     </nav-bar>
     <div class="flex-row">
       <div class="flex-item-20-percent">
         <ul>
           <template repeat="{{ metric in isolate.dartMetrics.values }}">
             <template if="{{ metric == selectedMetric }}">
               <li class="selected">
                 {{ metric.name }}
               </li>
@@ skipping 96 matching lines @@
       .graph {
         min-height: 600px;
       }
     </style>
     <div id="graph" class="graph">
     </div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="metrics.dart"></script>