Switch to standard integer types in ios/.

ios/web/web_state/global_web_state_event_tracker.h

 // Copyright 2015 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 IOS_WEB_WEB_STATE_GLOBAL_WEB_STATE_EVENT_TRACKER_H_
 #define IOS_WEB_WEB_STATE_GLOBAL_WEB_STATE_EVENT_TRACKER_H_
 
+#include <stddef.h>
+
 #include "base/macros.h"
 #include "base/observer_list.h"
 #include "ios/web/public/web_state/global_web_state_observer.h"
 
 namespace base {
 template <typename T>
 struct DefaultSingletonTraits;
 }  // namespace base
 
 namespace web {
@@ skipping 33 matching lines @@
 
   // List of observers currently registered with the tracker.
   base::ObserverList<GlobalWebStateObserver, true> observer_list_;
 
   DISALLOW_COPY_AND_ASSIGN(GlobalWebStateEventTracker);
 };
 
 }  // namespace web
 
 #endif  // IOS_WEB_WEB_STATE_GLOBAL_WEB_STATE_EVENT_TRACKER_H_