Rework how ServiceObjects are created and cached in Observatory.

runtime/vm/object.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 3841 matching lines @@
 
   const Error& err = Error::Handle(EnsureIsFinalized(Isolate::Current()));
   if (!err.IsNull()) {
     jsobj.AddProperty("error", err);
   }
   jsobj.AddProperty("implemented", is_implemented());
   jsobj.AddProperty("abstract", is_abstract());
   jsobj.AddProperty("patch", is_patch());
   jsobj.AddProperty("finalized", is_finalized());
   jsobj.AddProperty("const", is_const());
-  jsobj.AddProperty("super", Class::Handle(SuperClass()));
+  const Class& superClass = Class::Handle(SuperClass());
+  if (!superClass.IsNull()) {
+    jsobj.AddProperty("super", superClass);
+  }
   jsobj.AddProperty("library", Object::Handle(library()));
   const Script& script = Script::Handle(this->script());
   if (!script.IsNull()) {
     intptr_t line_number = 0;
     intptr_t column_number = 0;
     script.GetTokenLocation(token_pos(), &line_number, &column_number);
     jsobj.AddProperty("script", script);
     jsobj.AddProperty("line", line_number);
     jsobj.AddProperty("col", column_number);
   }
@@ skipping 14082 matching lines @@
   return "_MirrorReference";
 }
 
 
 void MirrorReference::PrintToJSONStream(JSONStream* stream, bool ref) const {
   Instance::PrintToJSONStream(stream, ref);
 }
 
 
 }  // namespace dart