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

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

 <link rel="import" href="../../../../packages/polymer/polymer.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">
 <link rel="import" href="script_ref.html">
 
 <polymer-element name="code-view" extends="observatory-element">
   <template>
     <link rel="stylesheet" href="css/shared.css">
@@ skipping 79 matching lines @@
           <div class="memberName">Inclusive</div>
           <div class="memberValue">{{ code.formattedInclusiveTicks }}</div>
         </div>
         <div class="memberItem">
           <div class="memberName">Exclusive</div>
           <div class="memberValue">{{ code.formattedExclusiveTicks }}</div>
         </div>
         <div class="memberItem">
           <div class="memberName">Constant object pool</div>
           <div class="memberValue">
-            <instance-ref ref="{{ code.objectPool }}"></instance-ref>
+            <any-service-ref ref="{{ code.objectPool }}"></any-service-ref>
           </div>
         </div>
       </div>
     </div>
     <hr>
     <div class="content">
       <template if="{{ code.hasDisassembly }}">
         <div class="flex-row">
             <div class="flex-item-fixed-2-12 memberHeader">Inclusive</div>
             <div class="flex-item-fixed-2-12 memberHeader">Exclusive</div>
@@ skipping 50 matching lines @@
               {{ instruction.human }}
             </div>
           </template>
         </div>
       </template>
     </div>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="code_view.dart"></script>