Simplify the user agent code some more since after r255534 it's not affected by the site's URL.

content/public/common/content_switches.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 "content/public/common/content_switches.h"
 
 #include "base/command_line.h"
 
 namespace switches {
 
@@ skipping 893 matching lines @@
 // Use fake device for MediaStream to replace actual camera and microphone.
 const char kUseFakeDeviceForMediaStream[] = "use-fake-device-for-media-stream";
 
 // Bypass the media stream infobar by selecting the default device for media
 // streams (e.g. WebRTC). Works with --use-fake-device-for-media-stream.
 const char kUseFakeUIForMediaStream[]     = "use-fake-ui-for-media-stream";
 
 // Set when Chromium should use a mobile user agent.
 const char kUseMobileUserAgent[] = "use-mobile-user-agent";
 
-// A string used to override the default user agent with a custom one.
-const char kUserAgent[]                     = "user-agent";
-
 // On POSIX only: the contents of this flag are prepended to the utility
 // process command line. Useful values might be "valgrind" or "xterm -e gdb
 // --args".
 const char kUtilityCmdPrefix[]              = "utility-cmd-prefix";
 
 // Causes the process to run as a utility subprocess.
 const char kUtilityProcess[]                = "utility";
 
 // The utility process is sandboxed, with access to one directory. This flag
 // specifies the directory that can be accessed.
@@ skipping 112 matching lines @@
 #endif
 
 #if defined(OS_POSIX)
 // Causes the child processes to cleanly exit via calling exit().
 const char kChildCleanExit[]                = "child-clean-exit";
 #endif
 
 // Don't dump stuff here, follow the same order as the header.
 
 }  // namespace switches