Add PlatformWindow/Event related code for Ozone X11.

ui/platform_window/x11/BUILD.gn

 # 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/ui.gni")
+import("//ui/ozone/ozone.gni")
 
-assert(use_x11)
+assert(use_x11 || ozone_platform_x11)
 
 component("x11") {
   output_name = "x11_window"
 
   deps = [
     "//base",
     "//skia",
     "//ui/events",
     "//ui/events/devices",
     "//ui/events/platform",
     "//ui/events/platform/x11",
     "//ui/gfx/x",
     "//ui/platform_window",
   ]
 
   configs += [ "//build/config/linux:x11" ]
 
   defines = [ "X11_WINDOW_IMPLEMENTATION" ]
 
   sources = [
-    "x11_window.cc",
-    "x11_window.h",
+    "x11_window_base.cc",
+    "x11_window_base.h",
     "x11_window_export.h",
   ]
+
+  if (ozone_platform_x11) {
+    sources += [
+      "x11_window_ozone.cc",
+      "x11_window_ozone.h",
+    ]
+  } else if (use_x11) {
+    sources += [
+      "x11_window.cc",
+      "x11_window.h",
+    ]
+  }
 }