Make callers of CommandLine use it via the base:: namespace.

chrome/browser/ui/webui/options/chromeos/guest_mode_options_ui_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 "base/command_line.h"
 #include "chrome/browser/ui/webui/options/options_ui_browsertest.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/test/base/testing_profile.h"
 #include "chromeos/chromeos_switches.h"
 #include "chromeos/login/user_names.h"
 
 namespace {
 
 // Same as OptionsUIBrowserTest but launches with Guest mode command line
 // switches.
 class GuestModeOptionsBrowserTest : public options::OptionsUIBrowserTest {
  public:
   GuestModeOptionsBrowserTest() : OptionsUIBrowserTest() {}
 
-  virtual void SetUpCommandLine(CommandLine* command_line) override {
+  virtual void SetUpCommandLine(base::CommandLine* command_line) override {
     command_line->AppendSwitch(chromeos::switches::kGuestSession);
     command_line->AppendSwitchASCII(chromeos::switches::kLoginUser,
                                     chromeos::login::kGuestUserName);
     command_line->AppendSwitchASCII(chromeos::switches::kLoginProfile,
                                     TestingProfile::kTestUserProfileDir);
     command_line->AppendSwitch(switches::kIncognito);
   }
 };
 
 IN_PROC_BROWSER_TEST_F(GuestModeOptionsBrowserTest, LoadOptionsByURL) {
   NavigateToSettings();
   VerifyTitle();
   VerifyNavbar();
 }
 
 }  // namespace