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

ui/ozone/ozone.gyp

Index: ui/ozone/ozone.gyp
diff --git a/ui/ozone/ozone.gyp b/ui/ozone/ozone.gyp
index 8ccb0d72723e38c9f426cc94d8e47447903ed391..ddff90abfe6f1e6ceb3e27f2839629414690fa4a 100644
--- a/ui/ozone/ozone.gyp
+++ b/ui/ozone/ozone.gyp
@@ -41,6 +41,9 @@
         'ozone_platform.h',
         'ozone_switches.cc',
         'ozone_switches.h',
+        'platform/dri/chromeos/display_event_listener.h',
+        'platform/dri/chromeos/display_event_listener_udev.cc',
+        'platform/dri/chromeos/display_event_listener_udev.h',
         'platform/dri/chromeos/display_mode_dri.cc',
         'platform/dri/chromeos/display_mode_dri.h',
         'platform/dri/chromeos/display_snapshot_dri.cc',
@@ -126,6 +129,11 @@
             '<(DEPTH)/ui/display/display.gyp:display_types',
           ],
         }],
+        ['use_udev == 0', {
+          'sources/': [
+            ['exclude', '_udev\\.(h|cc)$'],
+          ],
+        }],
       ]
     },
   ],