Add a working command line debugger to Observatory.

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 15 matching lines @@
       nav ul:after {
         content: ""; clear: both; display: block;
       }
       .vertical-spacer {
         height: 40px;
         background-color: #0489c3;
       }
     </style>
     <nav>
       <ul>
-        <nav-notify events="{{ app.notifications }}"></nav-notify>
+        <template if="{{ showNotify }}">
+          <nav-notify events="{{ app.notifications }}"></nav-notify>
+        </template>
         <content></content>
       </ul>
     </nav>
     <div class="vertical-spacer">
     </div>
     <template if="{{ pad }}">
       <br>
     </template>
   </template>
 </polymer-element>
@@ skipping 220 matching lines @@
 
 <polymer-element name="nav-notify-item" extends="observatory-element">
   <template>
     <style>
       .item {
         position: relative;
         padding: 16px;
         margin-top: 10px;
         margin-right: 10px;
         padding-right: 25px;
-        width: 200px;
+        width: 225px;
         color: #ddd;
         background: rgba(0,0,0,.6);
         border: solid 2px white;
         box-shadow: 0 0 5px black;
         border-radius: 5px;
         animation: fadein 1s;
       }
 
       @keyframes fadein {
         from { opacity: 0; }
@@ skipping 28 matching lines @@
     </style>
     <template if="{{ event.eventType == 'IsolateInterrupted' ||
                      event.eventType == 'BreakpointReached' ||
                      event.eventType == 'ExceptionThrown' }}">
       <div class="item">
         Isolate
         <a class="link" on-click="{{ goto }}"
            _href="{{ gotoLink('/inspect', event.isolate) }}">{{ event.isolate.name }}</a>
         is paused
         <template if="{{ event.breakpoint != null }}">
-          at breakpoint
+          at breakpoint {{ event.breakpoint['breakpointNumber'] }}
         </template>
         <template if="{{ event.eventType == 'ExceptionThrown' }}">
           at exception
         </template>
 
         <br><br>
-        <action-link callback="{{ resume }}" label="resume" color="white">
-        </action-link>
-        <action-link callback="{{ stepInto }}" label="step" color="white">
-        </action-link>
-        <action-link callback="{{ stepOver }}" label="step&nbsp;over"
-                     color="white"></action-link>
-        <action-link callback="{{ stepOut }}" label="step&nbsp;out"
-                     color="white"></action-link>
+        [<a class="link" on-click="{{ goto }}"
+            _href="{{ gotoLink('/debugger', event.isolate) }}">debug</a>]
+
         <a class="boxclose" on-click="{{ closeItem }}">&times;</a>
       </div>
     </template>
     <template if="{{ event.eventType == 'VMDisconnected' }}">
       <div class="item">
         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>