use_x11 is better than is_linux for xdisplaycheck dep in mandoline gn build

mandoline/BUILD.gn

 # Copyright 2015 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/ui.gni")
+
 group("all") {
   # Meta-target, don't link into production code.
   testonly = true
 
   deps = [
     ":tests",
   ]
 
   if (!is_component_build) {
     deps += [ "//mandoline/app" ]
   }
 }
 
 group("tests") {
   testonly = true
   deps = [
     "//mojo:tests",
   ]
 
-  if (is_linux) {
+  if (use_x11) {
     deps += [ "//tools/xdisplaycheck" ]
   }
 
   # TODO(GYP): Make this work.
   if (!is_component_build && !is_mac) {
     deps += [
       "//components/clipboard:apptests",
       "//components/filesystem:apptests",
       "//components/html_viewer:apptests",
       "//components/html_viewer:html_viewer_unittests",
       "//components/resource_provider:apptests",
       "//components/resource_provider:resource_provider_unittests",
       "//components/view_manager:tests",
       "//mandoline/tab:mandoline_frame_apptests",
       "//mandoline/ui/browser:mandoline_browser_apptests",
       "//media/mojo/services:tests",
       "//sql/mojo:apptests",
     ]
   }
 }