Remember when an isolate was paused and subtly display it in Obseravatory

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 27 matching lines @@
     </div>
 
     <isolate-shared-summary isolate="{{ isolate }}"></isolate-shared-summary>
 
   </template>
 </polymer-element>
 
 <polymer-element name="isolate-run-state" extends="observatory-element">
   <template>
     <template if="{{ isolate.paused }}">
-      <strong>paused</strong>
+      <strong title="{{ isolate.pauseEvent.timestamp.toString() }}">paused</strong>
     </template>
 
     <template if="{{ isolate.running }}">
       <strong>running</strong>
     </template>
 
     <template if="{{ isolate.idle }}">
       <strong>idle</strong>
     </template>
 
@@ skipping 153 matching lines @@
   </template>
 </polymer-element>
 
 <polymer-element name="isolate-counter-chart" extends="observatory-element">
   <template>
     <div id="counterPieChart" style="height: 200px"></div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="isolate_summary.dart"></script>