Use PlatformThreadId, not int when dealing with thread ids.

base/platform_thread_posix.cc

 // 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.
 
 #include "base/platform_thread.h"
 
 #include <errno.h>
 #include <sched.h>
 
 #if defined(OS_MACOSX)
@@ skipping 10 matching lines @@
 #endif
 
 static void* ThreadFunc(void* closure) {
   PlatformThread::Delegate* delegate =
       static_cast<PlatformThread::Delegate*>(closure);
   delegate->ThreadMain(); 
   return NULL;
 }
 
 // static
-int PlatformThread::CurrentId() {
+PlatformThreadId PlatformThread::CurrentId() {
   // Pthreads doesn't have the concept of a thread ID, so we have to reach down
   // into the kernel.
 #if defined(OS_MACOSX)
   return mach_thread_self();
 #elif defined(OS_LINUX)
   return syscall(__NR_gettid);
 #endif
 }
 
 // static
@@ skipping 46 matching lines @@
   success = !pthread_create(thread_handle, &attributes, ThreadFunc, delegate);
 
   pthread_attr_destroy(&attributes);
   return success;
 }
 
 // static
 void PlatformThread::Join(PlatformThreadHandle thread_handle) {
   pthread_join(thread_handle, NULL);
 }