Use a direct include of strings headers in remoting/.

remoting/protocol/auth_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 "remoting/protocol/auth_util.h"
 
 #include "base/base64.h"
 #include "base/logging.h"
-#include "base/string_util.h"
+#include "base/strings/string_util.h"
 #include "crypto/hmac.h"
 #include "crypto/sha2.h"
 #include "net/base/net_errors.h"
 #include "net/socket/ssl_socket.h"
 
 namespace remoting {
 namespace protocol {
 
 const char kClientAuthSslExporterLabel[] =
     "EXPORTER-remoting-channel-auth-client";
@@ skipping 43 matching lines @@
   if (!response.Sign(shared_secret, out_bytes, kAuthDigestLength)) {
     NOTREACHED() << "HMAC::Sign failed";
     return std::string();
   }
 
   return std::string(out_bytes, out_bytes + kAuthDigestLength);
 }
 
 }  // namespace protocol
 }  // namespace remoting