ozone: evdev: Add gamepad support

ui/events/ozone/gamepad/gamepad_observer.h

Index: ui/events/ozone/gamepad/gamepad_observer.h
diff --git a/ui/events/ozone/gamepad/gamepad_observer.h b/ui/events/ozone/gamepad/gamepad_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..312f0d162f1f9cb6565611614f0aa6b2d127fa2f
--- /dev/null
+++ b/ui/events/ozone/gamepad/gamepad_observer.h
@@ -0,0 +1,27 @@
+// Copyright 2017 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_GAMEPAD_GAMEPAD_OBSERVER_H_
+#define UI_EVENTS_OZONE_GAMEPAD_GAMEPAD_OBSERVER_H_
+
+#include "base/logging.h"
+#include "base/time/time.h"
+#include "ui/events/ozone/gamepad/gamepad_event.h"
+
+namespace ui {
+
+class GamepadObserver {
+ public:
+  // Callback function when connected gamepad devices is updated.
+  virtual void OnGamepadDevicesUpdated() {}
+
+  // Callback function on gamepad.
+  virtual void OnGamepadEvent(const GamepadEvent& event) {}
+
+  virtual ~GamepadObserver() {}
+};
+
+}  // namespace ui
+
+#endif  // UI_EVENTS_OZONE_GAMEPAD_GAMEPAD_OBSERVER_H_