Cleanup: Pass std::string as const reference if possible

net/udp/udp_socket_perftest.cc

 // Copyright 2015 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 "base/basictypes.h"
 #include "base/bind.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "base/test/perf_time_logger.h"
@@ skipping 34 matching lines @@
   // has effect on Windows.
   void WriteBenchmark(bool use_nonblocking_io);
 
  protected:
   static const int kPacketSize = 1024;
   scoped_refptr<IOBufferWithSize> buffer_;
   base::WeakPtrFactory<UDPSocketPerfTest> weak_factory_;
 };
 
 // Creates and address from an ip/port and returns it in |address|.
-void CreateUDPAddress(std::string ip_str, uint16 port, IPEndPoint* address) {
+void CreateUDPAddress(const std::string& ip_str,
+                      uint16 port,
+                      IPEndPoint* address) {
   IPAddressNumber ip_number;
   bool rv = ParseIPLiteralToNumber(ip_str, &ip_number);
   if (!rv)
     return;
   *address = IPEndPoint(ip_number, port);
 }
 
 void UDPSocketPerfTest::WritePacketsToSocket(UDPClientSocket* socket,
                                              int num_of_packets,
                                              base::Closure done_callback) {
@@ skipping 64 matching lines @@
 #if defined(OS_WIN)
 TEST_F(UDPSocketPerfTest, WriteNonBlocking) {
   base::PerfTimeLogger timer("UDP_socket_write_nonblocking");
   WriteBenchmark(true);
 }
 #endif
 
 }  // namespace
 
 }  // namespace net