Clean up header files.

components/variations/metrics_util.cc

 // Copyright (c) 2012 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 "components/variations/metrics_util.h"
 
+#include <string.h>
+
 #include "base/sha1.h"
 #include "base/sys_byteorder.h"
 
 namespace metrics {
 
 uint32_t HashName(const std::string& name) {
   // SHA-1 is designed to produce a uniformly random spread in its output space,
   // even for nearly-identical inputs.
   unsigned char sha1_hash[base::kSHA1Length];
   base::SHA1HashBytes(reinterpret_cast<const unsigned char*>(name.c_str()),
                       name.size(),
                       sha1_hash);
 
   uint32_t bits;
   static_assert(sizeof(bits) < sizeof(sha1_hash), "more data required");
   memcpy(&bits, sha1_hash, sizeof(bits));
 
   return base::ByteSwapToLE32(bits);
 }
 
 }  // namespace metrics