Add is_chromecast to GN build.

ui/ozone/platform/drm/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/linux/pkg_config.gni")
 import("//ui/ozone/ozone.gni")
 
 declare_args() {
   use_mesa_platform_null = false
   use_drm_atomic = false
@@ skipping 82 matching lines @@
     "host/drm_overlay_manager.h",
     "host/drm_window_host.cc",
     "host/drm_window_host.h",
     "host/drm_window_host_manager.cc",
     "host/drm_window_host_manager.h",
     "ozone_platform_gbm.cc",
     "ozone_platform_gbm.h",
   ]
 
   deps = [
-    ":drm_common",
     "//base",
     "//ipc",
     "//skia",
     "//third_party/minigbm",
     "//ui/base",
     "//ui/display/types",
     "//ui/display/util",
     "//ui/events",
     "//ui/events/devices",
     "//ui/events/ozone:events_ozone_evdev",
     "//ui/events/ozone:events_ozone_layout",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
 
-  configs = [ ":libdrm" ]
+  configs += [ ":libdrm" ]
 
   public_configs = [ "//third_party/khronos:khronos_headers" ]
 
   defines = []
 
   if (use_drm_atomic) {
     defines += [ "USE_DRM_ATOMIC" ]
     sources += [
       "gpu/hardware_display_plane_atomic.cc",
       "gpu/hardware_display_plane_atomic.h",
@@ skipping 25 matching lines @@
 
   deps = [
     "//skia",
     "//testing/gtest",
     "//ui/gfx",
     "//ui/ozone",
   ]
 
   public_configs = [ ":libdrm" ]
 }