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

runtime/vm/intrinsifier_arm.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_ARM.
 #if defined(TARGET_ARCH_ARM)
 
 #include "vm/intrinsifier.h"
 
 #include "vm/assembler.h"
@@ skipping 1605 matching lines @@
   // Set Isolate::user_tag_.
   __ str(R2, Address(R1, Isolate::user_tag_offset()));
   __ Ret();
 }
 
 
 void Intrinsifier::UserTag_defaultTag(Assembler* assembler) {
   Isolate* isolate = Isolate::Current();
   // Set return value to default tag address.
   __ LoadImmediate(R0,
-      reinterpret_cast<uword>(isolate->object_store()) +
-                              ObjectStore::default_tag_offset());
+         reinterpret_cast<uword>(isolate) + Isolate::default_tag_offset());
   __ ldr(R0, Address(R0, 0));
   __ Ret();
 }
 
 
 void Intrinsifier::Profiler_getCurrentTag(Assembler* assembler) {
   // R1: Default tag address.
   Isolate* isolate = Isolate::Current();
   __ LoadImmediate(R1, reinterpret_cast<uword>(isolate));
   // Set return value to Isolate::current_tag_.
   __ ldr(R0, Address(R1, Isolate::current_tag_offset()));
   __ Ret();
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM