Add breadcrumb for the VM.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="action_link.html">
 <link rel="import" href="observatory_element.html">
 
 <polymer-element name="nav-bar" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
       nav {
         position: fixed;
@@ skipping 159 matching lines @@
 
 <polymer-element name="top-nav-menu">
   <template>
     <nav-menu link="/vm" anchor="Observatory" last="{{ last }}">
       <nav-menu-item link="/vm-connect" anchor="Connect to a different VM"></nav-menu-item>
       <content></content>
     </nav-menu>
   </template>
 </polymer-element>
 
+<polymer-element name="vm-nav-menu">
+  <template>
+    <nav-menu link="/vm" anchor="{{ vm.target.name }}" last="{{ last }}">
+      <template repeat="{{ isolate in vm.isolates }}">
+        <nav-menu-item link="{{ makeLink('/inspect', isolate) }}"
+                       anchor="{{ isolate.name }}"></nav-menu-item>
+      </template>
+      <content></content>
+    </nav-menu>
+  </template>
+</polymer-element>
+
 <polymer-element name="isolate-nav-menu" extends="observatory-element">
   <template>
     <nav-menu link="{{ makeLink('/inspect', isolate) }}" anchor="{{ isolate.name }}" last="{{ last }}">
       <nav-menu-item link="{{ makeLink('/debugger', isolate) }}"
                      anchor="debugger"></nav-menu-item>
       <nav-menu-item link="{{ makeLink('/profiler', isolate) }}"
                      anchor="cpu profile"></nav-menu-item>
       <nav-menu-item link="{{ makeLink('/allocation-profiler', isolate) }}"
                      anchor="allocation profile"></nav-menu-item>
       <nav-menu-item link="{{ makeLink('/heap-map', isolate) }}"
@@ skipping 129 matching lines @@
         Disconnected from VM
         <br><br>
         <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
       </div>
     </template>
   </template>
 </polymer-element>
 
 
 <script type="application/dart" src="nav_bar.dart"></script>