Reland "ozone: Build with xkbcommon by default on is_linux && !is_chromecast"

This reverts commit b7edadd9.

Reason for revert: MSAN issue fixed

Original change's description:
> Revert "ozone: Build with xkbcommon by default on is_linux && !is_chromecast"
> 
> This reverts commit 713420fb.
> 
> Reason for revert: Causes MSAN failure
> More details in crbug/1027853
> 
> Original change's description:
> > ozone: Build with xkbcommon by default on is_linux && !is_chromecast
> > 
> > This is necessary on Linux targets unless you don't want keyboard
> > support or only need support for a hardcoded US layout.
> > 
> > Noticed because the CQ broke after building for ozone locally. This
> > reduces the number of flags needed to build as the Linux Ozone builder
> > does.
> > 
> > Bug: 1026476
> > 
> > Change-Id: I77352c133b1f7552301b6e1f252d40a4f2c72106
> > 
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1925370
> > Reviewed-by: Scott Violet <sky@chromium.org>
> > Reviewed-by: Kevin Schoedel <kpschoedel@chromium.org>
> > Commit-Queue: Michael Spang <spang@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#718240}
> 
> TBR=sky@chromium.org,spang@chromium.org,kpschoedel@chromium.org
> 
> Change-Id: I4fa0de1881acbf1eaf7e70bfe4b24dbc84647f43
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 1026476
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1932436
> Reviewed-by: Tim Schumann <tschumann@chromium.org>
> Commit-Queue: Tim Schumann <tschumann@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#718445}

TBR=sky@chromium.org,spang@chromium.org,kpschoedel@chromium.org,tschumann@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1026476, 1027853
Change-Id: I4f601a169bd5d18714a1a78ca8cacd0b43939afa
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1941277Reviewed-by: Michael Spang <spang@chromium.org>
Commit-Queue: Michael Spang <spang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719850}

ui/base/ui_features.gni

@@ -6,7 +6,7 @@ import("//build/config/ui.gni")
 
 declare_args() {
   # Optional system library.
-  use_xkbcommon = false
+  use_xkbcommon = use_ozone && is_linux && !is_chromecast
 
   # Whether the platform provides a native accessibility toolkit.
   has_native_accessibility = use_atk || is_win || is_mac