GN: Set and use use_clipboard_aurax11 correctly

ui/base/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/buildflag_header.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
 import("//ui/base/ui_features.gni")
@@ skipping 571 matching lines @@
       "models/button_menu_item_model.cc",
       "models/dialog_model.cc",
       "theme_provider.cc",
       "touch/touch_editing_controller.cc",
       "ui_base_types.cc",
     ]
   }
 
   # Aura clipboard.
   if (use_aura) {
-    if (use_x11) {
+    if (use_clipboard_aurax11) {
       sources += [
         "clipboard/clipboard_aurax11.cc",
         "clipboard/clipboard_aurax11.h",
       ]
     } else if (!is_win && !is_android) {
       # This file is used for all non-X11, non-Windows, non-Android aura Builds.
       sources += [
         "clipboard/clipboard_aura.cc",
         "clipboard/clipboard_aura.h",
       ]
@@ skipping 342 matching lines @@
 if (is_mac) {
   mac_framework_bundle("ui_unittests_framework") {
     testonly = true
     deps = [
       "//ui/resources:ui_test_pak_bundle_data",
     ]
     info_plist = "test/framework-Info.plist"
     output_name = "ui_unittests Framework"
   }
 }