ChromeOS shouldn't build non-Ozone/X11.

ChromeOS switched to Ozone quite some time ago and
no longer supports non-Ozone/X11. However, when I started to
enable use_ozone for is_linux, is_chromeos started to build use_x11
as well, which is not correct.

Atm, use_x11 is not built for is_chromeos, because
use_ozone = is_chromeos, and this line is just redundant.

Bug: None
Change-Id: I38ad54cd2febd5a8cce57bc29d092525e07cb715
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2353265
Auto-Submit: Maksim Sisov (GMT+3) <msisov@igalia.com>
Commit-Queue: Dirk Pranke <dpranke@google.com>
Reviewed-by: Dirk Pranke <dpranke@google.com>
Cr-Commit-Position: refs/heads/master@{#798172}

build/config/ui.gni

@@ -42,7 +42,7 @@ declare_args() {
 # These variables depend on other variables and can't be set externally.
 
 # Indicates if the UI toolkit depends on X11.
-use_x11 = (is_linux || is_chromeos) && !use_ozone
+use_x11 = is_linux && !use_ozone
 
 # Make sure glib is not used if building for ChromeOS/Chromecast
 assert(!use_glib || (is_linux && !is_chromeos && !is_chromecast))