Codechange: deduplicate tick-handlers of all video drivers

They were all identical, so better put this in a single place
hoping it is less likely to break.

src/video/video_driver.hpp

@@ -189,6 +189,17 @@ protected:
 	 */
 	virtual void CheckPaletteAnim() {}
 
+	/**
+	 * Run the game for a single tick, processing boththe game-tick and draw-tick.
+	 * @returns True if the driver should redraw the screen.
+	 */
+	bool Tick();
+
+	/**
+	 * Sleep till the next tick is about to happen.
+	 */
+	void SleepTillNextTick();
+
 	std::chrono::steady_clock::duration GetGameInterval()
 	{
 		return std::chrono::milliseconds(MILLISECONDS_PER_TICK);
@@ -198,6 +209,10 @@ protected:
 	{
 		return std::chrono::microseconds(1000000 / _settings_client.gui.refresh_rate);
 	}
+
+	std::chrono::steady_clock::time_point last_realtime_tick;
+	std::chrono::steady_clock::time_point next_game_tick;
+	std::chrono::steady_clock::time_point next_draw_tick;
 };
 
 #endif /* VIDEO_VIDEO_DRIVER_HPP */