Use a direct include of strings headers in chromeos/.

chromeos/dbus/audio_node.cc

 // Copyright (c) 2013 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 "chromeos/dbus/audio_node.h"
 
 #include "base/format_macros.h"
-#include "base/stringprintf.h"
 #include "base/strings/string_number_conversions.h"
+#include "base/strings/stringprintf.h"
 
 namespace chromeos {
 
 AudioNode::AudioNode()
     : is_input(false),
       id(0),
       active(false),
       plugged_time(0) {
 }
 
@@ skipping 18 matching lines @@
                       "active = %s ",
                       active ? "true" : "false");
   base::StringAppendF(&result,
                       "plugged_time= %s ",
                       base::Uint64ToString(plugged_time).c_str());
 
   return result;
 }
 
 }  // namespace chromeos