Make ui::InputDeviceEventObserver provide a default implementation

ui/events/devices/x11/device_data_manager_x11_unittest.cc

Index: ui/events/devices/x11/device_data_manager_x11_unittest.cc
diff --git a/ui/events/devices/x11/device_data_manager_x11_unittest.cc b/ui/events/devices/x11/device_data_manager_x11_unittest.cc
index 75a43d147a781adc0c80c1ca82b1a3e76d49e1ef..444611f4fcc6b25da67d9168c54d9ba1020fce74 100644
--- a/ui/events/devices/x11/device_data_manager_x11_unittest.cc
+++ b/ui/events/devices/x11/device_data_manager_x11_unittest.cc
@@ -35,12 +35,9 @@ class TestInputDeviceObserver : public InputDeviceEventObserver {
   }
 
   // InputDeviceEventObserver implementation.
-  void OnTouchscreenDeviceConfigurationChanged() override {}
   void OnKeyboardDeviceConfigurationChanged() override {
     change_notified_ = true;
   }
-  void OnMouseDeviceConfigurationChanged() override {}
-  void OnTouchpadDeviceConfigurationChanged() override {}
 
   int change_notified() const { return change_notified_; }
   void Reset() { change_notified_ = false; }