Ensure Freed TLS Slots Contain nullptr on Reallocation

base/threading/thread_local_storage.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BASE_THREADING_THREAD_LOCAL_STORAGE_H_
 #define BASE_THREADING_THREAD_LOCAL_STORAGE_H_
 
+#include <stdint.h>
+
 #include "base/atomicops.h"
 #include "base/base_export.h"
 #include "base/macros.h"
 #include "build/build_config.h"
 
 #if defined(OS_WIN)
 #include <windows.h>
 #elif defined(OS_POSIX)
 #include <pthread.h>
 #endif
@@ skipping 98 matching lines @@
     // value 'value'.
     void Set(void* value);
 
     bool initialized() const {
       return base::subtle::Acquire_Load(&initialized_) != 0;
     }
 
     // The internals of this struct should be considered private.
     base::subtle::Atomic32 initialized_;
     int slot_;
+    uint32_t version_;
   };
 
   // A convenience wrapper around StaticSlot with a constructor. Can be used
   // as a member variable.
   class BASE_EXPORT Slot {
    public:
     explicit Slot(TLSDestructorFunc destructor = NULL);
     ~Slot();
 
     // Get the thread-local value stored in this slot.
     // Values are guaranteed to initially be zero.
     void* Get() const;
 
     // Set the slot's thread-local value to |value|.
     void Set(void* value);
 
    private:
     StaticSlot tls_slot_;
 
     DISALLOW_COPY_AND_ASSIGN(Slot);
   };
 
  private:
   DISALLOW_COPY_AND_ASSIGN(ThreadLocalStorage);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREADING_THREAD_LOCAL_STORAGE_H_