Revert of Move JoinString to the base namespace

chrome/browser/extensions/extension_startup_browsertest.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 <vector>
 
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/path_service.h"
@@ skipping 49 matching lines @@
           base::StringPrintf(
               "%s/%s/",
               chrome_prefs::internals::kSettingsEnforcementTrialName,
               chrome_prefs::internals::kSettingsEnforcementGroupNoEnforcement));
 #if defined(OFFICIAL_BUILD) && defined(OS_WIN)
       // In Windows official builds, it is not possible to disable settings
       // authentication.
       unauthenticated_load_allowed_ = false;
 #endif
     } else {
-      base::FilePath::StringType paths =
-          base::JoinString(load_extensions_,
-                           base::FilePath::StringType(1, ','));
+      base::FilePath::StringType paths = JoinString(load_extensions_, ',');
       command_line->AppendSwitchNative(switches::kLoadExtension,
                                        paths);
       command_line->AppendSwitch(switches::kDisableExtensionsFileAccessCheck);
     }
   }
 
   bool SetUpUserDataDirectory() override {
     base::FilePath profile_dir;
     PathService::Get(chrome::DIR_USER_DATA, &profile_dir);
     profile_dir = profile_dir.AppendASCII(TestingProfile::kTestUserProfileDir);
@@ skipping 216 matching lines @@
         .AppendASCII("extensions")
         .AppendASCII("app2");
     load_extensions_.push_back(fourth_extension_path.value());
   }
 };
 
 IN_PROC_BROWSER_TEST_F(ExtensionsLoadMultipleTest, Test) {
   WaitForServicesToStart(4, true);
   TestInjection(true, true);
 }