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

runtime/vm/object_store.h

 // 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.
 
 #ifndef VM_OBJECT_STORE_H_
 #define VM_OBJECT_STORE_H_
 
 #include "vm/object.h"
 
 namespace dart {
@@ skipping 414 matching lines @@
     empty_uint32_array_ = array.raw();
   }
 
   RawFunction* handle_message_function() const {
     return handle_message_function_;
   }
   void set_handle_message_function(const Function& function) {
     handle_message_function_ = function.raw();
   }
 
-  RawUserTag* default_tag() const {
-    return default_tag_;
-  }
-  void set_default_tag(const UserTag& tag) {
-    // Only set once.
-    ASSERT(default_tag_ == UserTag::null());
-    ASSERT(!tag.IsNull());
-    default_tag_ = tag.raw();
-  }
-  static intptr_t default_tag_offset() {
-    return OFFSET_OF(ObjectStore, default_tag_);
-  }
-
   RawArray* library_load_error_table() const {
     return library_load_error_table_;
   }
   void set_library_load_error_table(const Array& table) {
     library_load_error_table_ = table.raw();
   }
   static intptr_t library_load_error_table_offset() {
     return OFFSET_OF(ObjectStore, library_load_error_table_);
   }
 
@@ skipping 79 matching lines @@
   RawString* unhandled_exception_handler_;
   RawContext* empty_context_;
   RawInstance* stack_overflow_;
   RawInstance* out_of_memory_;
   RawUnhandledException* preallocated_unhandled_exception_;
   RawStacktrace* preallocated_stack_trace_;
   RawFunction* lookup_port_handler_;
   RawTypedData* empty_uint32_array_;
   RawFunction* handle_message_function_;
   RawArray* library_load_error_table_;
-  RawUserTag* default_tag_;
   RawObject** to() {
     return reinterpret_cast<RawObject**>(&library_load_error_table_);
   }
 
   friend class SnapshotReader;
 
   DISALLOW_COPY_AND_ASSIGN(ObjectStore);
 };
 
 }  // namespace dart
 
 #endif  // VM_OBJECT_STORE_H_