Rework the format of the FlagList response.

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="view_footer.html">
 
 <polymer-element name="flag-list" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <nav-bar>
       <top-nav-menu></top-nav-menu>
       <nav-menu link="{{ makeLink('/flags') }}" anchor="flags" last="{{ true }}"></nav-menu>
       <nav-refresh callback="{{ refresh }}"></nav-refresh>
     </nav-bar>
 
     <div class="content-centered">
-      <template if="{{ flagList['modifiedFlags'].isNotEmpty }}">
+      <template if="{{ modifiedFlags.isNotEmpty }}">
         <h1>Modified Flags</h1>
         <br>
-        <template repeat="{{ flag in flagList['modifiedFlags'] }}">
+        <template repeat="{{ flag in modifiedFlags }}">
           <flag-item flag="{{ flag }}"></flag-item>
           <br>
         </template>
         <hr>
       </template>
 
       <h1>Unmodified Flags</h1>
       <br>
-      <template if="{{ flagList['unmodifiedFlags'].isEmpty }}">
+      <template if="{{ unmodifiedFlags.isEmpty }}">
         <em>None</em>
       </template>
-      <template if="{{ flagList['unmodifiedFlags'].isNotEmpty }}">
-        <template repeat="{{ flag in flagList['unmodifiedFlags'] }}">
+      <template if="{{ unmodifiedFlags.isNotEmpty }}">
+        <template repeat="{{ flag in unmodifiedFlags }}">
           <flag-item flag="{{ flag }}"></flag-item>
           <br>
         </template>
       </template>
     </div>
     <view-footer></view-footer>
   </template>
 </polymer-element>
 
 <polymer-element name="flag-item" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <span style="color:#aaa">// {{ flag['comment'] }}</span>
     <div style="padding: 3px 0">
       <b>{{ flag['name'] }}</b>
       &nbsp;=&nbsp;
       {{ flag['valueAsString'] }}
     </div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="flag_list.dart"></script>