Refactor 'dart:profiler' UserTag API

runtime/vm/isolate.h

 // 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.
 
 #ifndef VM_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "platform/thread.h"
@@ skipping 474 matching lines @@
   }
   static intptr_t current_tag_offset() {
     return OFFSET_OF(Isolate, current_tag_);
   }
 
   RawGrowableObjectArray* tag_table() const { return tag_table_; }
   void set_tag_table(const GrowableObjectArray& value);
 
   RawUserTag* current_tag() const { return current_tag_; }
   void set_current_tag(const UserTag& tag);
-  void clear_current_tag();
 
 #if defined(DEBUG)
 #define REUSABLE_HANDLE_SCOPE_ACCESSORS(object)                                \
   void set_reusable_##object##_handle_scope_active(bool value) {               \
     reusable_##object##_handle_scope_active_ = value;                          \
   }                                                                            \
   bool reusable_##object##_handle_scope_active() const {                       \
     return reusable_##object##_handle_scope_active_;                           \
   }
   REUSABLE_HANDLE_LIST(REUSABLE_HANDLE_SCOPE_ACCESSORS)
@@ skipping 214 matching lines @@
   char* script_url_;
   char* library_url_;
   char* class_name_;
   char* function_name_;
   char* exception_callback_name_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_