Cleanup: Pass std::string as const reference from content/

content/browser/renderer_host/p2p/socket_host_test_utils.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 "content/browser/renderer_host/p2p/socket_host_test_utils.h"
 
 #include "base/sys_byteorder.h"
 #include "base/thread_task_runner_handle.h"
 #include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
@@ skipping 190 matching lines @@
 }
 
 void CreateStunResponse(std::vector<char>* packet) {
   CreateStunPacket(packet, kStunBindingResponse);
 }
 
 void CreateStunError(std::vector<char>* packet) {
   CreateStunPacket(packet, kStunBindingError);
 }
 
-net::IPEndPoint ParseAddress(const std::string ip_str, uint16 port) {
+net::IPEndPoint ParseAddress(const std::string& ip_str, uint16 port) {
   net::IPAddressNumber ip;
   EXPECT_TRUE(net::ParseIPLiteralToNumber(ip_str, &ip));
   return net::IPEndPoint(ip, port);
 }