Codechange: remove _realtime_tick variable

(cherry picked from commit fe451b8dc7)

# Conflicts:
#	src/debug.cpp
#	src/debug.h
#	src/video/video_driver.cpp

src/debug.cpp

@@ -60,8 +60,6 @@ std::string _loadgame_DBGL_data;
 bool _save_DBGC_data = false;
 std::string _loadgame_DBGC_data;
 
-uint32 _realtime_tick = 0;
-
 struct DebugLevel {
 	const char *name;
 	int *level;

src/debug.h

@@ -131,9 +131,6 @@ void CDECL ShowInfoF(const char *str, ...) WARN_FORMAT(1, 2);
 
 const char *GetLogPrefix();
 
-/** The real time in the game. */
-extern uint32 _realtime_tick;
-
 void ClearDesyncMsgLog();
 void LogDesyncMsg(std::string msg);
 char *DumpDesyncMsgLog(char *buffer, const char *last);

src/video/video_driver.cpp

@@ -19,13 +19,6 @@ bool VideoDriver::Tick()
 {
 	auto cur_ticks = std::chrono::steady_clock::now();
 
-	/* If more than a millisecond has passed, increase the _realtime_tick. */
-	if (cur_ticks - this->last_realtime_tick > std::chrono::milliseconds(1)) {
-		auto delta = std::chrono::duration_cast<std::chrono::milliseconds>(cur_ticks - this->last_realtime_tick);
-		_realtime_tick += delta.count();
-		this->last_realtime_tick += delta;
-	}
-
 	if (cur_ticks >= this->next_game_tick || (_fast_forward && !_pause_mode)) {
 		if (_fast_forward && !_pause_mode) {
 			this->next_game_tick = cur_ticks + this->GetGameInterval();

src/video/video_driver.hpp

@@ -210,7 +210,6 @@ 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;
 };