iwyu: Cleanup in the following files:

chrome/browser/autofill/autofill_metrics.h

 // Copyright (c) 2011 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 CHROME_BROWSER_AUTOFILL_AUTOFILL_METRICS_H_
 #define CHROME_BROWSER_AUTOFILL_AUTOFILL_METRICS_H_
 #pragma once
 
+#include <stddef.h>
 #include <string>
 
 #include "base/basictypes.h"
 
 class AutofillMetrics {
  public:
   // Each of these is logged at most once per form submission.
   enum CreditCardInfoBarMetric {
     // Logged when we show an infobar prompting to save credit card info.
     CREDIT_CARD_INFOBAR_SHOWN = 0,
@@ skipping 60 matching lines @@
   virtual void Log(ServerQueryMetric metric) const;
 
   // This should be called at most once per run.
   virtual void LogStoredProfileCount(size_t num_profiles) const;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(AutofillMetrics);
 };
 
 #endif  // CHROME_BROWSER_AUTOFILL_AUTOFILL_METRICS_H_