ozone: evdev: Add gamepad support

ui/events/devices/device_hotplug_event_observer.h

Index: ui/events/devices/device_hotplug_event_observer.h
diff --git a/ui/events/devices/device_hotplug_event_observer.h b/ui/events/devices/device_hotplug_event_observer.h
index 7b846bc426aa101a127d37c49c6377295f63d042..ad957fba34eba848552cf62216019c90422bf41f 100644
--- a/ui/events/devices/device_hotplug_event_observer.h
+++ b/ui/events/devices/device_hotplug_event_observer.h
@@ -40,6 +40,11 @@ class EVENTS_DEVICES_EXPORT DeviceHotplugEventObserver {
   virtual void OnTouchpadDevicesUpdated(
       const std::vector<InputDevice>& devices) = 0;
 
+  // On a hotplug event this is called with the list of available gamepads.The
+  // set of gamepads may not have changed.
+  virtual void OnGamepadDevicesUpdated(
+      const std::vector<InputDevice>& devices) = 0;
+
   // On completion of the initial startup scan. This means all of the above
   // OnDevicesUpdated() methods have been called with a complete list.
   virtual void OnDeviceListsComplete() = 0;