Use a direct include of strings headers in remoting/.

remoting/host/heartbeat_sender.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/host/heartbeat_sender.h"
 
 #include <math.h>
 
 #include "base/bind.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/rand_util.h"
-#include "base/string_number_conversions.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/strings/stringize_macros.h"
 #include "base/time.h"
 #include "remoting/base/constants.h"
 #include "remoting/host/server_log_entry.h"
 #include "remoting/jingle_glue/iq_sender.h"
 #include "remoting/jingle_glue/signal_strategy.h"
 #include "third_party/libjingle/source/talk/xmllite/xmlelement.h"
 #include "third_party/libjingle/source/talk/xmpp/constants.h"
 
 using buzz::QName;
@@ skipping 240 matching lines @@
 
   std::string message = signal_strategy_->GetLocalJid() + ' ' +
       base::IntToString(sequence_id_);
   std::string signature(key_pair_->SignMessage(message));
   signature_tag->AddText(signature);
 
   return signature_tag.Pass();
 }
 
 }  // namespace remoting