1. Add user tag to the pointers traversed in the object store

runtime/lib/profiler.cc

 // Copyright (c) 2014, 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/bootstrap_natives.h"
 
 #include "include/dart_api.h"
 
 #include "vm/exceptions.h"
 #include "vm/native_entry.h"
@@ skipping 27 matching lines @@
   const UserTag& old = UserTag::Handle(isolate->current_tag());
   self.MakeActive();
   return old.raw();
 }
 
 
 DEFINE_NATIVE_ENTRY(UserTag_defaultTag, 0) {
   if (FLAG_trace_intrinsified_natives) {
     OS::Print("UserTag_defaultTag\n");
   }
-  return isolate->object_store()->default_tag();
+  return isolate->default_tag();
 }
 
 
 DEFINE_NATIVE_ENTRY(Profiler_getCurrentTag, 0) {
   if (FLAG_trace_intrinsified_natives) {
     OS::Print("Profiler_getCurrentTag\n");
   }
   return isolate->current_tag();
 }
 
 
 }  // namespace dart