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

ui/events/ozone/device/device_event_observer.h

+// Copyright 2014 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.
+
+#ifndef UI_EVENTS_OZONE_DEVICE_EVENT_OBSERVER_H_
+#define UI_EVENTS_OZONE_DEVICE_EVENT_OBSERVER_H_
+
+#include "ui/events/events_export.h"
+
+namespace ui {
+
+class DeviceEvent;
+
+class EVENTS_EXPORT DeviceEventObserver {
+ public:
+  virtual ~DeviceEventObserver() {}
+
+  virtual void OnDeviceEvent(const DeviceEvent& event) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_DEVICE_EVENT_OBSERVER_H_
+