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

ui/native_theme/native_theme_switches.cc

 // Copyright 2014 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 "ui/native_theme/native_theme_switches.h"
 
 namespace switches {
 
 // Enables overlay scrollbars on Aura or Linux. Does nothing on Mac.
 const char kEnableOverlayScrollbar[] = "enable-overlay-scrollbar";
 
 // Disables overlay scrollbars on Aura or Linux. Does nothing on Mac.
 const char kDisableOverlayScrollbar[] = "disable-overlay-scrollbar";
 
 }  // namespace switches
 
 namespace ui {
 
 bool IsOverlayScrollbarEnabled() {
-  const CommandLine& command_line = *CommandLine::ForCurrentProcess();
+  const base::CommandLine& command_line =
+      *base::CommandLine::ForCurrentProcess();
 
   if (command_line.HasSwitch(switches::kDisableOverlayScrollbar))
     return false;
   else if (command_line.HasSwitch(switches::kEnableOverlayScrollbar))
     return true;
 
   return false;
 }
 
 }  // namespace ui