Add persistent handles to service protocol and Observatory UI

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="action_link.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="isolate_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="script_inset.html">
 <link rel="import" href="script_ref.html">
 <polymer-element name="isolate-summary" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
@@ skipping 150 matching lines @@
             See <a on-click="{{ goto }}" _href="{{ gotoLink('/metrics', isolate) }}">metrics</a>
           </div>
         </div>
         <div class="memberItem">
           <div class="memberValue">
             See <a on-click="{{ goto }}" _href="{{ gotoLink('/heap-snapshot', isolate) }}">heap snapshot</a>
           </div>
         </div>
         <div class="memberItem">
           <div class="memberValue">
+            See <a on-click="{{ goto }}" _href="{{ gotoLink('/persistent-handles', isolate) }}">persistent handles</a>
+          </div>
+        </div>
+        <div class="memberItem">
+          <div class="memberValue">
             See <a on-click="{{ goto }}" _href="{{ gotoLink('/ports', isolate) }}">ports</a>
           </div>
         </div>
         <div class="memberItem">
           <div class="memberValue">
             See <a on-click="{{ goto }}" _href="{{ gotoLink('/logging', isolate) }}">logging</a>
           </div>
         </div>
         <!-- Temporarily disabled until UI for dart:io is acceptable.
         <template if="{{ isolate.ioEnabled }}">
@@ skipping 32 matching lines @@
     <div class="chart-wrapper" id="isolate-counter-chart">
       <div class="chart-host-wrapper">
         <div class="chart-host" id="isolate-counter-chart-host"></div>
         <div class="chart-legend-host" id="isolate-counter-chart-legend-host"></div>
       </div>
   </div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="isolate_summary.dart"></script>