[Chromecast] Correct some Cast dependencies in //chrome/browser/ui.

ui/events/devices/x11/BUILD.gn

 # Copyright 2016 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")
+import("//ui/ozone/ozone.gni")
+
+assert(use_x11 || ozone_platform_x11)
 
 component("x11") {
   output_name = "events_devices_x11"
 
   sources = [
     "device_data_manager_x11.cc",
     "device_data_manager_x11.h",
     "device_list_cache_x11.cc",
     "device_list_cache_x11.h",
     "events_devices_x11_export.h",
@@ skipping 11 matching lines @@
     "//skia",
     "//ui/display",
     "//ui/events:events_base",
     "//ui/events/devices",
     "//ui/events/keycodes:x11",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gfx/x",
   ]
 }