Add breadcrumb for the VM.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 
 <!-- TODO(turnidge): Use core-icon once core_elements work properly in
      devtools -->
 <polymer-element name="icon-expand-less" noscript>
@@ skipping 91 matching lines @@
         overflow-y: auto;
       }
       .commandline {
         flex: 0 0 auto;
       }
     </style>
 
     <div class="container">
       <nav-bar id="navbarDiv" showNotify="{{ false }}">
         <top-nav-menu></top-nav-menu>
-        <isolate-nav-menu isolate="{{ isolate }}">
-        </isolate-nav-menu>
+        <vm-nav-menu vm="{{ isolate.vm }}"></vm-nav-menu>
+        <isolate-nav-menu isolate="{{ isolate }}"></isolate-nav-menu>
         <nav-menu link="{{ makeLink('/debugger', isolate) }}" anchor="debugger" last="{{ true }}"></nav-menu>
       </nav-bar>
       <div id="stackDiv" class="stack">
         <debugger-stack id="stackElement" isolate="{{ isolate }}"></debugger-stack>
       </div>
       <!--
       <core-splitter direction="up" allowOverflow=true></core-splitter>
       -->
       <div id="splitterDiv"><hr class="splitter"></div>
       <div id="consoleDiv" class="console">
@@ skipping 189 matching lines @@
         margin: 20px;
         font: 400 16px consolas, courier, monospace;
         width: 95%;
       }
     </style>
     <input id="textBox" class="textBox" type="text" value="{{ text }}" autofocus>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="debugger.dart"></script>