Give fields a model class in the service library.

runtime/bin/vmservice/observatory/lib/src/elements/class_view.html

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="curly_block.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="library_ref.html">
 <link rel="import" href="nav_bar.html">
 <link rel="import" href="observatory_element.html">
@@ skipping 90 matching lines @@
       <template if="{{ cls.fields.isNotEmpty }}">
         fields ({{ cls.fields.length }})
         <curly-block expand="{{ cls.fields.length <= 8 }}">
           <div class="memberList">
             <template repeat="{{ field in cls.fields }}">
               <div class="memberItem">
                 <div class="memberName">
                   <field-ref ref="{{ field }}"></field-ref>
                 </div>
                 <div class="memberValue">
-                  <template if="{{ field['value'] != null }}">
-                    <any-service-ref ref="{{ field['value'] }}"></any-service-ref>
+                  <template if="{{ field.value != null }}">
+                    <any-service-ref ref="{{ field.value }}"></any-service-ref>
                   </template>
                 </div>
               </div>
             </template>
           </div>
         </curly-block><br><br>
       </template>
 
       <template if="{{ cls.functions.isNotEmpty }}">
         functions ({{ cls.functions.length }})
@@ skipping 69 matching lines @@
                   startPos="{{ cls.tokenPos }}"
                   endPos="{{ cls.endTokenPos }}">
     </script-inset>
 
     <br><br><br><br>
     <br><br><br><br>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="class_view.dart"></script>