X11 and Ozone: fix use_x11 && use_x11 build for UIControlsAura

When use_x11 && use_ozone are set to true at the same
time, compiler throws an error about multiple definitions
of the CreateUIControlsAura.

Thus, to fix that, create a separate source file for
is_linux case that will choose what class to
use based on the IsUsingOzonePlatform feature flag.

Please note that this is a temp solution and it will
be removed once use_x11 goes away.

PS: this patch uses the same approach used in other patches.
For example, https://crrev.com/c/2247719
PPS: I didn't spot that in the beginning as linux-rel bot
couldn't compile use_x11 && use_ozone because of failures
in the chrome installer step. But after we fixed the sysroot,
I spotted some problems and fixing them now.

Bug: 1085700
Change-Id: I1c2f3a0762df4b195775d30f580df09090f13999
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2362698
Reviewed-by: Scott Violet <sky@chromium.org>
Commit-Queue: Maksim Sisov (GMT+3) <msisov@igalia.com>
Cr-Commit-Position: refs/heads/master@{#799289}

diff --git a/ui/aura/BUILD.gn b/ui/aura/BUILD.gn
index 5edf943..0b7516f 100644
--- a/ui/aura/BUILD.gn
+++ b/ui/aura/BUILD.gn

@@ -247,9 +247,14 @@
     sources += [ "test/ui_controls_factory_aurawin.cc" ]
   }
 
+  if (is_linux) {
+    sources += [ "test/ui_controls_factory_aura_linux.cc" ]
+  }
+
   if (use_x11) {
     sources += [
-      "test/ui_controls_factory_aurax11.cc",
+      "test/ui_controls_aurax11.cc",
+      "test/ui_controls_aurax11.h",
       "test/x11_event_sender.cc",
       "test/x11_event_sender.h",
     ]
@@ -264,7 +269,10 @@
     if (is_fuchsia) {
       deps += [ "//ui/ozone" ]
     }
-    sources += [ "test/ui_controls_factory_ozone.cc" ]
+    sources += [
+      "test/ui_controls_ozone.cc",
+      "test/ui_controls_ozone.h",
+    ]
   }
 
   if (is_linux || is_chromeos) {