Remember when a variable has been expanded/unexpanded in the debugger.

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="eval_link.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 -->
@@ skipping 252 matching lines @@
                             inDebuggerContext="{{ true }}"
                             variables="{{ frame.variables }}">
               </source-inset>
             </div>
             <div class="flex-item-vars">
               <div style="padding:10px;" class="memberList">
                 <template repeat="{{ v in frame.variables }}">
                   <div class="memberItem">
                     <div class="memberName">{{ v['name']}}</div>
                     <div class="memberValue">
-                      <any-service-ref ref="{{ v['value'] }}">
+                      <any-service-ref ref="{{ v['value'] }}"
+                                       expandKey="{{ makeExpandKey(v['name']) }}">
                       </any-service-ref>
                     </div>
                   </div>
                 </template>
               </div>
             </div>
           </div>
           <!-- TODO(turnidge): Add eval box here? -->
           <div class="frameContractor">
             <template if="{{expanded}}">
@@ skipping 161 matching lines @@
         padding: 5px;
         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>