Move JoinString to the base namespace

chrome/installer/setup/update_active_setup_version_work_item.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 "chrome/installer/setup/update_active_setup_version_work_item.h"
 
 #include <stdint.h>
 
 #include <vector>
 
@@ skipping 51 matching lines @@
   if (operation_ == UPDATE_AND_BUMP_OS_UPGRADES_COMPONENT) {
     uint32_t previous_value;
     if (!base::StringToUint(version_components[OS_UPGRADES], &previous_value)) {
       LOG(WARNING) << "Couldn't process previous OS_UPGRADES Active Setup "
                       "version component: " << version_components[OS_UPGRADES];
       previous_value = 0;
     }
     version_components[OS_UPGRADES] = base::UintToString16(previous_value + 1);
   }
 
-  return JoinString(version_components, L',');
+  return base::JoinString(version_components, L",");
 }