gn build: check use_udev before depending on udev

chrome/browser/ui/BUILD.gn

 # 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.
 
 import("//build/config/crypto.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 
 gypi_values = exec_script("//build/gypi_to_gn.py",
                           [ rebase_path("../../chrome_browser_ui.gypi") ],
@@ skipping 367 matching lines @@
   }
   if (is_desktop_linux) {
     sources += rebase_path(gypi_values.chrome_browser_ui_desktop_linux_sources,
                            ".",
                            "//chrome")
   }
   if (is_linux) {  # Both desktop Linux and ChromeOS.
     sources += rebase_path(gypi_values.chrome_browser_ui_linux_sources,
                            ".",
                            "//chrome")
-    deps += [ "//device/udev_linux" ]
     if (use_aura) {
       configs += [ "//build/config/linux:fontconfig" ]
       deps += [ "//dbus" ]
     }
     if (use_x11) {
       sources += rebase_path(gypi_values.chrome_browser_ui_x11_sources,
                              ".",
                              "//chrome")
       configs += [ "//build/config/linux:x11" ]
       deps += [ "//ui/events/devices" ]
       if (is_chromeos) {
         sources -= [ "views/tabs/window_finder_x11.cc" ]
       }
     }
   }
 
+  if (use_udev) {
+    deps += [ "//device/udev_linux" ]
+  }
+
   if (enable_app_list) {
     sources += rebase_path(gypi_values.chrome_browser_ui_app_list_sources,
                            ".",
                            "//chrome")
     deps += [ "//ui/app_list" ]
   } else {
     sources += rebase_path(gypi_values.chrome_browser_ui_non_app_list_sources,
                            ".",
                            "//chrome")
   }
@@ skipping 111 matching lines @@
     "//chrome/browser",
     "//content/public/browser",
     "//content/public/common",
     "//content/test:test_support",
     "//net:test_support",
     "//skia",
     "//testing/gtest",
     "//ui/base",
   ]
 }