Include parent field/list index in retaining path.

runtime/bin/vmservice/client/lib/src/elements/instance_view.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="class_ref.html">
 <link rel="import" href="error_view.html">
 <link rel="import" href="eval_box.html">
 <link rel="import" href="eval_link.html">
 <link rel="import" href="field_ref.html">
 <link rel="import" href="function_ref.html">
 <link rel="import" href="instance_ref.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="nav_bar.html">
@@ skipping 63 matching lines @@
                            label="[find]"
                            expr="10">
                 </eval-link>
               </template>
               <template if="{{ path != null }}">
                 <template repeat="{{ element in path['elements'] }}">
                 <div class="memberItem">
                   <div class="memberName">[{{ element['index']}}]</div>
                   <div class="memberValue">
                     <instance-ref ref="{{ element['value'] }}"></instance-ref>
+                    <template if="{{ element['parentField'] != null }}">
+                      in <field-ref ref="{{ element['parentField'] }}"></field-ref>
+                    </template>
+                    <template if="{{ element['parentListIndex'] != null }}">
+                      at list index {{ element['parentListIndex'] }} of
+                    </template>
                   </div>
                   </div>
                 </template>
                 <template if="{{ path['length'] > path['elements'].length }}">
                   showing {{ path['elements'].length }} of {{ path['length'] }}
                   <eval-link
                     callback="{{ retainingPath }}"
                     label="[find more]"
                     expr="{{ path['elements'].length * 2 }}">
                   </eval-link>
@@ skipping 90 matching lines @@
         <eval-box callback="{{ eval }}"></eval-box>
       </div>
       <br><br><br><br>
       <br><br><br><br>
 
     </template>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="instance_view.dart"></script>