Refactor Udev device support in Ozone and add a DRM hotplug monitor

ui/events/events.gyp

Index: ui/events/events.gyp
diff --git a/ui/events/events.gyp b/ui/events/events.gyp
index 00f5186c113e982ef979faed938d2b54bd78c02d..a76bdf8a9fa03eec726cc8d2cadbb5d45bdef555 100644
--- a/ui/events/events.gyp
+++ b/ui/events/events.gyp
@@ -141,9 +141,13 @@
         'ozone/evdev/key_event_converter_evdev.h',
         'ozone/evdev/touch_event_converter_evdev.cc',
         'ozone/evdev/touch_event_converter_evdev.h',
+        'ozone/device_udev.cc',
+        'ozone/device_udev.h',
         'ozone/event_factory_ozone.cc',
         'ozone/event_factory_ozone.h',
         'ozone/events_ozone.cc',
+        'ozone/monitor_udev.h',
+        'ozone/scoped_udev.h',
         'platform/platform_event_dispatcher.h',
         'platform/platform_event_observer.h',
         'platform/platform_event_source.cc',
@@ -223,9 +227,8 @@
           ],
         }],
         ['use_udev==0', {
-          'sources!': [
-            'ozone/evdev/device_manager_udev.cc',
-            'ozone/evdev/device_manager_udev.h',
+          'sources/': [
+            ['exclude', '_udev\\.(h|cc)$'],
           ],
         }],
       ],