Make udev target disappear on linux when use_udev==0

chrome/chrome_browser_ui.gypi

 # Copyright 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.
 
 {
   'variables': {
     'chrome_browser_ui_non_ios_sources': [
       'browser/ui/accelerator_utils.h',
       'browser/ui/android/android_about_app_info.cc',
       'browser/ui/android/android_about_app_info.h',
@@ skipping 2870 matching lines @@
                 ['exclude', '^browser/ui/views/'],
               ]
             }],
           ],
         }],
         ['desktop_linux==1', {
           'sources': [ '<@(chrome_browser_ui_desktop_linux_sources)' ],
         }],
         ['OS=="linux"', {  # Both desktop Linux and ChromeOS.
           'sources': [ '<@(chrome_browser_ui_linux_sources)' ],
-          'dependencies': [
-            '../build/linux/system.gyp:udev',
-          ],
           'conditions': [
             ['use_aura==1', {
               'dependencies': [
                 '../build/linux/system.gyp:dbus',
                 '../build/linux/system.gyp:fontconfig',
                 '../dbus/dbus.gyp:dbus',
               ],
             }],
             # x11 build
             ['use_x11==1', {
               'sources': [ '<@(chrome_browser_ui_x11_sources)' ],
               'dependencies': [
                 '../build/linux/system.gyp:x11',
                 '../build/linux/system.gyp:gio',
               ],
             }],
+            ['use_udev==1', {
+              'dependencies': [
+                '../build/linux/system.gyp:udev',
+              ],
+            }],
           ],
         }],
         ['enable_app_list==1', {
           'sources': [ '<@(chrome_browser_ui_app_list_sources)' ],
           'dependencies': [
             '../ui/app_list/app_list.gyp:app_list',
           ],
         }, {
           'sources': [ '<@(chrome_browser_ui_non_app_list_sources)' ],
         }],
@@ skipping 38 matching lines @@
         }],
         ['OS!="android" and OS!="ios"', {
           'dependencies': [
             '../device/bluetooth/bluetooth.gyp:device_bluetooth',
           ],
         }],
       ],
     },
   ],
 }