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

runtime/vm/intrinsifier_x64.cc

 // Copyright (c) 2013, 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/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1518 matching lines @@
   // Set Isolate::user_tag_.
   __ movq(Address(RBX, Isolate::user_tag_offset()), R10);
   __ ret();
 }
 
 
 void Intrinsifier::UserTag_defaultTag(Assembler* assembler) {
   // RBX: Address of default tag.
   Isolate* isolate = Isolate::Current();
   const Immediate& default_tag_addr =
-      Immediate(reinterpret_cast<int64_t>(isolate->object_store()) +
-                                          ObjectStore::default_tag_offset());
+      Immediate(reinterpret_cast<int64_t>(isolate) +
+                Isolate::default_tag_offset());
   __ movq(RBX, default_tag_addr);
   // Set return value.
   __ movq(RAX, Address(RBX, 0));
   __ ret();
 }
 
 
 void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
   // RBX: Isolate.
   Isolate* isolate = Isolate::Current();
   const Immediate& isolate_address =
       Immediate(reinterpret_cast<int64_t>(isolate));
   __ movq(RBX, isolate_address);
   // Set return value to Isolate::current_tag_.
   __ movq(RAX, Address(RBX, Isolate::current_tag_offset()));
   __ ret();
 }
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64