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

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

 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="curly_block.html">
 <link rel="import" href="observatory_element.html">
 <link rel="import" href="service_ref.html">
 
 <polymer-element name="instance-ref" extends="service-ref">
   <template>
     <link rel="stylesheet" href="css/shared.css">
     <style>
       .errorBox {
         background-color: #f5f5f5;
         border: 1px solid #ccc;
         padding: 10px;
         font-family: consolas, courier, monospace;
         font-size: 1em;
         line-height: 1.2em;
         white-space: pre;
       }
     </style>
     <span>
-      <template if="{{ isError(ref) }}">
-         <pre class="errorBox">{{ ref.message }}</pre>
+      <template if="{{ ref.isSentinel }}">
+        <div title="{{ hoverText }}">{{ ref.valueAsString }}</div>
       </template>
 
-      <template if="{{ isUnexpected(ref) }}">
-        unexpected reference type &lt;{{ ref.serviceType }}&gt;
+      <template if="{{ ref.isString || ref.isBool || ref.isInt || ref.isDouble || ref.isNull }}">
+        <a on-click="{{ goto }}" _href="{{ url }}">{{ ref.valueAsString }}</a>
       </template>
 
-      <template if="{{ isSentinel(ref) }}">
-        <div title="{{ hoverText }}">{{ ref['valueAsString'] }}</div>
+      <template if="{{ ref.isType }}">
+        <a on-click="{{ goto }}" _href="{{ url }}">{{ ref.name }}</a>
       </template>
 
-      <template if="{{ (isString(ref) ||
-                        isBool(ref) ||
-                        isNull(ref) ||
-                        isInt(ref)) ||
-                        isDouble(ref)) }}">
-        <a on-click="{{ goto }}" _href="{{ url }}">{{ ref['valueAsString'] }}</a>
-      </template>
-
-      <template if="{{ (isType(ref)) }}">
-        <a on-click="{{ goto }}" _href="{{ url }}">{{ ref['user_name'] }}</a>
-      </template>
-
-      <template if="{{ isInstance(ref) &&
-                       ref['closureFunc'] != null}}">
+      <template if="{{ ref.isClosure }}">
         <a on-click="{{ goto }}" _href="{{ url }}">
           <!-- TODO(turnidge): Switch this to fully-qualified function -->
-          {{ ref['closureFunc'].name }}
+          {{ ref.closureFunc.name }}
         </a>
       </template>
 
-      <template if="{{ isInstance(ref) &&
-                       ref['closureFunc'] == null}}">
-        <a on-click="{{ goto }}" _href="{{ url }}"><em>{{ ref['class'].name }}</em></a>
+      <template if="{{ ref.isInstance && !ref.isClosure }}">
+        <a on-click="{{ goto }}" _href="{{ url }}"><em>{{ ref.clazz.name }}</em></a>
         <curly-block callback="{{ expander() }}">
           <div class="memberList">
-            <template repeat="{{ field in ref['fields'] }}">
+            <template repeat="{{ field in ref.fields }}">
               <div class="memberItem">
                 <div class="memberName">
                   {{ field['decl']['user_name'] }}
                 </div>
                 <div class="memberValue">
-                  <instance-ref ref="{{ field['value'] }}"></instance-ref>
+                  <any-service-ref ref="{{ field['value'] }}"></any-service-ref>
                 </div>
               </div>
             </template>
           </div>
         </curly-block>
       </template>
 
-      <template if="{{ isList(ref) }}">
-        <a on-click="{{ goto }}" _href="{{ url }}"><em>{{ ref['class'].name }}</em> ({{ ref['length']}})</a>
+      <template if="{{ ref.isList }}">
+        <a on-click="{{ goto }}" _href="{{ url }}"><em>{{ ref.clazz.name }}</em> ({{ ref.length }})</a>
         <curly-block callback="{{ expander() }}">
           <div class="memberList">
-            <template repeat="{{ element in ref['elements'] }}">
+            <template repeat="{{ element in ref.elements }}">
               <div class="memberItem">
                 <div class="memberName">[{{ element['index']}}]</div>
                 <div class="memberValue">
-                  <instance-ref ref="{{ element['value'] }}"></instance-ref>
+                  <any-service-ref ref="{{ element['value'] }}"></instance-ref>
                 </div>
               </div>
             </template>
           </div>
         </curly-block>
       </template>
     </span>
   </template>
 </polymer-element>
 
 <script type="application/dart" src="instance_ref.dart"></script>