Use PlatformThreadId, not int when dealing with thread ids.

base/non_thread_safe.h

 // Copyright (c) 2006-2008 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_NON_THREAD_SAFE_H__
 #define BASE_NON_THREAD_SAFE_H__
 
 #include "base/logging.h"
+#include "base/platform_thread.h"
 
 // A helper class used to help verify that methods of a class are
 // called from the same thread.  One can inherit from this class and use
 // CalledOnValidThread() to verify.
 //
 // This is intended to be used with classes that appear to be thread safe, but
 // aren't.  For example, a service or a singleton like the preferences system.
 //
 // Example:
 // class MyClass : public NonThreadSafe {
 //  public:
 //   void Foo() {
 //     DCHECK(CalledOnValidThread());
 //     ... (do stuff) ...
 //   }
 // }
 //
 // In Release mode, CalledOnValidThread will always return true.
 //
 #ifndef NDEBUG
 class NonThreadSafe {
  public:
   NonThreadSafe();
   ~NonThreadSafe();
 
  protected:
   bool CalledOnValidThread() const;
 
  private:
-  int valid_thread_id_;
+  PlatformThreadId valid_thread_id_;
 };
 #else
 // Do nothing in release mode.
 class NonThreadSafe {
  public:
   NonThreadSafe() {}
   ~NonThreadSafe() {}
 
  protected:
   bool CalledOnValidThread() const {
     return true;
   }
 };
 #endif  // NDEBUG
 
 #endif  // BASE_NON_THREAD_SAFE_H__