[Isolates]...

src/top.h

 // Copyright 2006-2008 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 359 matching lines @@
  private:
   // The context that initiated this JS execution.
   static ThreadLocalTop thread_local_;
   static void InitializeThreadLocal();
   static void PrintStackTrace(FILE* out, ThreadLocalTop* thread);
   static void MarkCompactPrologue(bool is_compacting,
                                   ThreadLocalTop* archived_thread_data);
   static void MarkCompactEpilogue(bool is_compacting,
                                   ThreadLocalTop* archived_thread_data);
 
-  // Debug.
-  // Mutex for serializing access to break control structures.
-  static Mutex* break_access_;
-
   friend class SaveContext;
   friend class AssertNoContextChange;
   friend class ExecutionAccess;
 
   static void FillCache();
 };
 
 
 // If the GCC version is 4.1.x or 4.2.x an additional field is added to the
 // class as a work around for a bug in the generated code found with these
@@ skipping 59 matching lines @@
 
 class ExecutionAccess BASE_EMBEDDED {
  public:
   ExecutionAccess();
   ~ExecutionAccess();
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_TOP_H_