Revert "Reland "Reland "X11 and Ozone: enable use_x11 and use_ozone"""

This reverts commit 8ce938a2.

Reason for revert: <Suspect this CL breaks Linux FYI Ozone bot and  Linux FYI SkiaRenderer Vulkan (NVIDIA)/(Intel HD 630) >

Original change's description:
> Reland "Reland "X11 and Ozone: enable use_x11 and use_ozone""
> 
> This is a reland of 75363679
> 
> Original change's description:
> > Reland "X11 and Ozone: enable use_x11 and use_ozone"
> > 
> > This is a reland of f985905e.
> > 
> > This change broke our headless build:
> > ERROR at //ui/events/platform/x11/BUILD.gn:51:5: Assertion failed.
> >     assert(ozone_platform_x11)
> >     ^-----
> > See //components/viz/demo/BUILD.gn:73:7: which caused the file to be included.
> >       "//ui/events/platform/x11",.
> > 
> > Fix:
> > Don't include x11 build for headless case.
> > 
> > Original change's description:
> > > X11 and Ozone: enable use_x11 and use_ozone
> > >
> > > This is the final change that enables use_x11
> > > and use_ozone for Linux builds and (as it was
> > > before) excludes X11 for chromeos, chromecast,
> > > lacros.
> > >
> > > in order to run ozone/X11/wayland, one must pass
> > > —enable-features=UseOzonePlatform
> > > —ozone-platform=x11 or wayland. otherwise,
> > > non-ozone/X11 is used.
> > >
> > > it’s also possible to completely disable X11
> > > so that clients, who need that kind of build can
> > > continue to have that.
> > >
> > > Bug: 1085700
> > > Change-Id: I171bcb53c406555a1d4bec3e88d76dc676310d48
> > > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2315869
> > > Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> > > Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
> > > Reviewed-by: Scott Violet <sky@chromium.org>
> > > Commit-Queue: Maksim Sisov (GMT+3) <msisov@igalia.com>
> > > Cr-Commit-Position: refs/heads/master@{#801523}
> > 
> > Bug: 1085700
> > Change-Id: I8bf0abead6c94c95ddc58443de7cf2268c977cf1
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2376806
> > Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> > Commit-Queue: Maksim Sisov (GMT+3) <msisov@igalia.com>
> > Cr-Commit-Position: refs/heads/master@{#801692}
> 
> Bug: 1085700
> Change-Id: Ia5ed2af9376354d3378d8edd98a7a1446f13c88b
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2379190
> Commit-Queue: Maksim Sisov (GMT+3) <msisov@igalia.com>
> Reviewed-by: Robert Kroeger <rjkroege@chromium.org>
> Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#802773}

TBR=rjkroege@chromium.org,sky@chromium.org,thomasanderson@chromium.org,msisov@igalia.com

Change-Id: I093bf5be51d6858d895c59d6bb31f3aa61c162b9
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 1085700
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2383110Reviewed-by: Maggie Chen <magchen@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802855}

build/args/headless.gn

@@ -45,6 +45,3 @@ v8_enable_lazy_source_positions = false
 use_glib = false
 use_gtk = false
 use_pangocairo = false
-
-# TODO(1096425): Remove this once use_x11 goes away.
-use_x11 = false

build/config/ui.gni

@@ -18,19 +18,11 @@
 # of //build/config/BUILDCONFIG.gn.
 
 import("//build/config/chromecast_build.gni")
-import("//build/config/chromeos/ui_mode.gni")
 
 declare_args() {
   # Indicates if Ozone is enabled. Ozone is a low-level library layer for Linux
-  # that does not require X11.
-  use_ozone =
-      is_chromeos || (is_chromecast && !is_android) || is_fuchsia || is_linux
-
-  # Indicates if the UI toolkit depends on X11.
-  # Enabled by default. Can be disabled if Ozone only build is required and
-  # vice-versa.
-  use_x11 =
-      is_linux && !is_chromecast && !is_chromeos && !chromeos_is_browser_only
+  # that does not require X11. Enabling this feature disables use of x11.
+  use_ozone = is_chromeos || (is_chromecast && !is_android) || is_fuchsia
 
   # Indicates if Aura is enabled. Aura is a low-level windowing library, sort
   # of a replacement for GDI or GTK.
@@ -45,6 +37,13 @@ declare_args() {
   use_glib = is_desktop_linux && !is_chromecast
 }
 
+# Additional dependent variables -----------------------------------------------
+#
+# These variables depend on other variables and can't be set externally.
+
+# Indicates if the UI toolkit depends on X11.
+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))