Coverity: Pass parameters by reference.

chrome/installer/util/google_chrome_distribution.cc

 // Copyright (c) 2011 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.
 //
 // This file defines specific implementation of BrowserDistribution class for
 // Google Chrome.
 
 #include "chrome/installer/util/google_chrome_distribution.h"
 
 #include <windows.h>
@@ skipping 485 matching lines @@
       product_guid());
 }
 
 // The functions below are not used by the 64-bit Windows binary -
 // see the comment in google_chrome_distribution_dummy.cc
 #ifndef _WIN64
 // A helper function that writes to HKLM if the handle was passed through the
 // command line, but HKCU otherwise. |experiment_group| is the value to write
 // and |last_write| is used when writing to HKLM to determine whether to close
 // the handle when done.
-void SetClient(std::wstring experiment_group, bool last_write) {
+void SetClient(const std::wstring& experiment_group, bool last_write) {
   static int reg_key_handle = -1;
   if (reg_key_handle == -1) {
     // If a specific Toast Results key handle (presumably to our HKLM key) was
     // passed in to the command line (such as for system level installs), we use
     // it. Otherwise, we write to the key under HKCU.
     const CommandLine& cmd_line = *CommandLine::ForCurrentProcess();
     if (cmd_line.HasSwitch(installer::switches::kToastResultsKey)) {
       // Get the handle to the key under HKLM.
       base::StringToInt(cmd_line.GetSwitchValueASCII(
           installer::switches::kToastResultsKey).c_str(),
@@ skipping 242 matching lines @@
   // we waited for chrome to exit so the uninstall would not detect chrome
   // running.
   bool system_level_toast = CommandLine::ForCurrentProcess()->HasSwitch(
       installer::switches::kSystemLevelToast);
 
   CommandLine cmd(InstallUtil::GetChromeUninstallCmd(system_level_toast,
                                                      GetType()));
   base::LaunchApp(cmd, false, false, NULL);
 }
 #endif