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

ui/ozone/ozone.gyp

 # Copyright 2013 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.
 
 {
   'variables': {
     'chromium_code': 1,
     'external_ozone_platforms': [],
     'external_ozone_platform_files': [],
     'external_ozone_platform_deps': [],
@@ skipping 108 matching lines @@
         }, {  # ozone_platform_test==0
           'sources/': [
             ['exclude', '^platform/test/'],
           ]
         }],
         ['chromeos==1', {
           'dependencies': [
             '<(DEPTH)/ui/display/display.gyp:display_types',
           ],
         }],
+        ['use_udev == 0', {
+          'sources/': [
+            ['exclude', '_udev\\.(h|cc)$'],
+          ],
+        }],
       ]
     },
   ],
 }