Factor ui::XWindow out of DesktopWindowTreeHostX11

This CL factors out most of DesktopWindowTreeHostX11 X11 code into a reusable
helper class, ui::XWindow. So that it can be re-used by Ozone/X11
PlatformWindow implementation.

It should not imply in any functional change.

Bug: 981606
Change-Id: I96735f1680c738723b2df9ac17928c09e0825f77
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1695008Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Commit-Queue: Nick Yamane <nickdiego@igalia.com>
Cr-Commit-Position: refs/heads/master@{#676967}

ui/base/x/BUILD.gn

@@ -21,6 +21,8 @@ jumbo_component("x") {
     "x11_util.cc",
     "x11_util.h",
     "x11_util_internal.h",
+    "x11_window.cc",
+    "x11_window.h",
     "x11_window_event_manager.cc",
     "x11_window_event_manager.h",
   ]
@@ -40,6 +42,7 @@ jumbo_component("x") {
     "//ui/events",
     "//ui/events/devices/x11",
     "//ui/events/keycodes:x11",
+    "//ui/events/x:x",
     "//ui/gfx",
     "//ui/gfx/x",
   ]

ui/views/widget/desktop_aura/desktop_screen_x11_unittest.cc

@@ -7,6 +7,7 @@
 #include <stdint.h>
 
 #include <memory>
+#include <vector>
 
 #include "base/macros.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -14,6 +15,8 @@
 #include "ui/aura/window.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/hit_test.h"
+#include "ui/base/x/x11_util.h"
+#include "ui/display/display.h"
 #include "ui/display/display_observer.h"
 #include "ui/events/test/event_generator.h"
 #include "ui/gfx/font_render_params.h"

ui/views/widget/desktop_aura/x11_desktop_handler.cc

@@ -10,6 +10,7 @@
 #include "ui/aura/env.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/base/x/x11_menu_list.h"
+#include "ui/base/x/x11_util.h"
 #include "ui/base/x/x11_window_event_manager.h"
 #include "ui/events/platform/platform_event_source.h"
 #include "ui/gfx/x/x11.h"