[Chromecast] Rename disable_display flag to is_cast_audio_only.

ui/ozone/ozone.gni

 # 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/chromecast_build.gni")
 import("//build/config/ui.gni")
 
 declare_args() {
   # Select platforms automatically. Turn this off for manual control.
   ozone_auto_platforms = use_ozone
@@ skipping 24 matching lines @@
     ozone_platform_headless = true
 
     if (is_chromecast) {
       # Enable the Cast ozone platform on all A/V Cast builds.
       ozone_platform_cast = true
 
       # For visual desktop Chromecast builds, override the default "headless"
       # platform with --ozone-platform=x11.
       # TODO(halliwell): Create a libcast_graphics implementation for desktop
       # using X11, and disable this platform.
-      if (is_cast_desktop_build && !disable_display) {
+      if (is_cast_desktop_build && !is_cast_audio_only) {
         ozone_platform_x11 = true
       } else {
         ozone_platform = "cast"
       }
     } else if (is_chromeos) {
       ozone_platform_gbm = true
       ozone_platform_x11 = true
     } else {
       # Build all platforms whose deps are in install-build-deps.sh.
       # Only these platforms will be compile tested by buildbots.
       ozone_platform_x11 = true
     }
   }
 }
 
 assert(use_ozone || !(ozone_platform_caca || ozone_platform_cast ||
                           ozone_platform_gbm || ozone_platform_headless ||
                           ozone_platform_x11 || ozone_platform_wayland),
        "Must set use_ozone to select ozone platforms")