Add PlatformWindow/Event related code for Ozone X11.

ui/ozone/platform/x11/BUILD.gn

+# Copyright 2016 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.
+
+source_set("x11") {
+  sources = [
+    "client_native_pixmap_factory_x11.cc",
+    "client_native_pixmap_factory_x11.h",
+    "ozone_platform_x11.cc",
+    "ozone_platform_x11.h",
+    "x11_surface_factory.cc",
+    "x11_surface_factory.h",
+  ]
+
+  deps = [
+    "//base",
+    "//ipc",
+    "//skia",
+    "//ui/base",
+    "//ui/display/types",
+    "//ui/display/util",
+    "//ui/events",
+    "//ui/events/devices",
+    "//ui/events/ozone:events_ozone",
+    "//ui/events/platform",
+    "//ui/events/platform/x11",
+    "//ui/events/x",
+    "//ui/gfx",
+    "//ui/gfx/geometry",
+    "//ui/gfx/x",
+    "//ui/ozone:ozone_base",
+    "//ui/platform_window/x11",
+  ]
+
+  configs += [ "//build/config/linux:x11" ]
+
+  public_configs = [ "//third_party/khronos:khronos_headers" ]
+}