Use PlatformThreadId, not int when dealing with thread ids.

base/thread.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_THREAD_H_
 #define BASE_THREAD_H_
 
 #include <string>
 
 #include "base/message_loop.h"
@@ skipping 84 matching lines @@
   //
   MessageLoop* message_loop() const { return message_loop_; }
 
   // Set the name of this thread (for display in debugger too).
   const std::string &thread_name() { return name_; }
 
   // The native thread handle.
   PlatformThreadHandle thread_handle() { return thread_; }
 
   // The thread ID.
-  int thread_id() const { return thread_id_; }
+  PlatformThreadId thread_id() const { return thread_id_; }
 
  protected:
   // Called just prior to starting the message loop
   virtual void Init() {}
 
   // Called just after the message loop ends
   virtual void CleanUp() {}
 
   static void SetThreadWasQuitProperly(bool flag);
   static bool GetThreadWasQuitProperly();
@@ skipping 11 matching lines @@
   StartupData* startup_data_;
 
   // The thread's handle.
   PlatformThreadHandle thread_;
 
   // The thread's message loop.  Valid only while the thread is alive.  Set
   // by the created thread.
   MessageLoop* message_loop_;
 
   // Our thread's ID.
-  int thread_id_;
+  PlatformThreadId thread_id_;
 
   // The name of the thread.  Used for debugging purposes.
   std::string name_;
 
   friend class ThreadQuitTask;
 
   DISALLOW_COPY_AND_ASSIGN(Thread);
 };
 
 }  // namespace base
 
 #endif  // BASE_THREAD_H_