Switch to standard integer types in base/.

base/synchronization/waitable_event_posix.cc

Index: base/synchronization/waitable_event_posix.cc
diff --git a/base/synchronization/waitable_event_posix.cc b/base/synchronization/waitable_event_posix.cc
index 696ffc7a02abe5a1c21e429032b217fd7f142c91..64d4376fe5654b486ea1e43cef7dc71a08fad215 100644
--- a/base/synchronization/waitable_event_posix.cc
+++ b/base/synchronization/waitable_event_posix.cc
@@ -2,13 +2,15 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <stddef.h>
+
 #include <algorithm>
 #include <vector>
 
 #include "base/logging.h"
-#include "base/synchronization/waitable_event.h"
 #include "base/synchronization/condition_variable.h"
 #include "base/synchronization/lock.h"
+#include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_restrictions.h"
 
 // -----------------------------------------------------------------------------