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

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

Index: runtime/bin/vmservice/observatory/lib/src/elements/eval_link.html
diff --git a/runtime/bin/vmservice/observatory/lib/src/elements/eval_link.html b/runtime/bin/vmservice/observatory/lib/src/elements/eval_link.html
index 21b11772336d0da9a150db62242f7f28bfea2e1b..d12f620aef3aee0f8be3e2b958348f391b7495d2 100644
--- a/runtime/bin/vmservice/observatory/lib/src/elements/eval_link.html
+++ b/runtime/bin/vmservice/observatory/lib/src/elements/eval_link.html
@@ -1,5 +1,6 @@
 <link rel="import" href="../../../../packages/polymer/polymer.html">
 <link rel="import" href="instance_ref.html">
+<link rel="import" href="error_ref.html">
 
 <polymer-element name="eval-link">
   <template>
@@ -21,7 +22,7 @@
       <span class="idle"><a on-click="{{ evalNow }}">{{ label }}</a></span>
     </template>
     <template if="{{ result != null }}">
-      = <instance-ref ref="{{ result }}"></instance-ref>
+      = <any-service-ref ref="{{ result }}"></any-service-ref>
     </template>
   </template>
 </polymer-element>