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

ui/ozone/platform/dri/chromeos/display_event_listener.h

Index: ui/ozone/platform/dri/chromeos/display_event_listener.h
diff --git a/ui/ozone/platform/dri/chromeos/display_event_listener.h b/ui/ozone/platform/dri/chromeos/display_event_listener.h
new file mode 100644
index 0000000000000000000000000000000000000000..a40df048b73ec841eb2e25495e3aefd0d1f8d957
--- /dev/null
+++ b/ui/ozone/platform/dri/chromeos/display_event_listener.h
@@ -0,0 +1,26 @@
+// 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_OZONE_PLATFORM_DRI_CHROMEOS_DISPLAY_EVENT_LISTENER_H_
+#define UI_OZONE_PLATFORM_DRI_CHROMEOS_DISPLAY_EVENT_LISTENER_H_
+
+#include "base/callback.h"
+
+namespace ui {
+
+typedef base::Callback<void()> DisplayEventCallback;
+
+// Interface for a display event listener.
+class DisplayEventListener {
+ public:
+  virtual ~DisplayEventListener() {}
+
+  // Caller will register a callback and start monitoring for display events.
+  // The monitor stops on destruction of the listener.
+  virtual void StartMonitoring(const DisplayEventCallback& callback) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_OZONE_PLATFORM_DRI_CHROMEOS_DISPLAY_EVENT_LISTENER_H_