Rewrite std::string("") to std::string(), Linux edition.

remoting/protocol/transport.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/transport.h"
 
 #include "base/logging.h"
 
 namespace remoting {
 namespace protocol {
 
 // static
 std::string TransportRoute::GetTypeString(RouteType type) {
   switch (type) {
     case DIRECT:
       return "direct";
     case STUN:
       return "stun";
     case RELAY:
       return "relay";
   }
   NOTREACHED();
-  return "";
+  return std::string();
 }
 
 TransportRoute::TransportRoute() : type(DIRECT) {
 }
 
 TransportRoute::~TransportRoute() {
 }
 
 }  // namespace protocol
 }  // namespace remoting