src/: Update the remaining include paths of string_split.h to its new location.

remoting/protocol/negotiating_authenticator.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/negotiating_authenticator.h"
 
 #include <algorithm>
 #include <sstream>
 
 #include "base/bind.h"
 #include "base/logging.h"
-#include "base/string_split.h"
+#include "base/strings/string_split.h"
 #include "crypto/rsa_private_key.h"
 #include "remoting/protocol/channel_authenticator.h"
 #include "remoting/protocol/v2_authenticator.h"
 #include "third_party/libjingle/source/talk/xmllite/xmlelement.h"
 
 namespace remoting {
 namespace protocol {
 
 namespace {
 
@@ skipping 215 matching lines @@
     current_authenticator_ = V2Authenticator::CreateForClient(
         AuthenticationMethod::ApplyHashFunction(
             current_method_.hash_function(),
             authentication_tag_, shared_secret_),
         initial_state);
   }
 }
 
 }  // namespace protocol
 }  // namespace remoting