Switch to standard integer types in base/trace_event/.

base/trace_event/trace_sampling_thread.cc

Index: base/trace_event/trace_sampling_thread.cc
diff --git a/base/trace_event/trace_sampling_thread.cc b/base/trace_event/trace_sampling_thread.cc
index 32ce7bde7693f265289fd6c82dc67f2e611f3dbd..ec4602ccc163924c54170b824b866440f2bb6102 100644
--- a/base/trace_event/trace_sampling_thread.cc
+++ b/base/trace_event/trace_sampling_thread.cc
@@ -2,9 +2,11 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "base/trace_event/trace_sampling_thread.h"
+#include <stddef.h>
+
 #include "base/trace_event/trace_event_impl.h"
 #include "base/trace_event/trace_log.h"
+#include "base/trace_event/trace_sampling_thread.h"
 
 namespace base {
 namespace trace_event {