Give instances their own model class; move DartErrors out of instance-ref into their own error-ref.

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 74 matching lines @@
         <template if="{{ cls.name != cls.vmName }}">
           <div class="memberItem">
             <div class="memberName">vm name</div>
             <div class="memberValue">{{ cls.vmName }}</div>
           </div>
         </template>
       </div>
     </div>
 
     <template if="{{ cls.error != null }}">
-      <!-- TODO(turnidge): Don't use instance-ref for error display here -->
-      <instance-ref ref="{{ cls.error }}"></instance-ref>
+      <error-ref ref="{{ cls.error }}"></error>
     </template>
 
     <hr>
 
     <div class="content">
       <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 }}">
-                    <instance-ref ref="{{ field['value'] }}"></instance-ref>
+                    <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 24 matching lines @@
             <div class="memberName">strongly reachable</div>
             <div class="memberValue">
               <template if="{{ instances == null }}">
                 <eval-link callback="{{ reachable }}"
                            label="[find]"
                            expr="100">
                 </eval-link>
               </template>
               <template if="{{ instances != null }}">
                 sample
-                <instance-ref ref="{{ instances['sample'] }}"></instance-ref>
+                <any-service-ref ref="{{ instances['sample'] }}"></any-service-ref>
                 <template if="{{ instances['totalCount'] > instances['sampleCount'] }}">
                   <eval-link callback="{{ reachable }}"
                            label="[more]"
                            expr="{{ instances['sampleCount'] * 2 }}">
                   </eval-link>
                 </template>
                 of total {{ instances['totalCount'] }}
               </template>
             </div>
           </div>
@@ skipping 24 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>