player/Control: convert `total_play_time` to `FloatDuration`

src/Stats.cxx

@@ -120,7 +120,7 @@ stats_print(Response &r, const Partition &partition)
 #else
 		 (unsigned)std::chrono::duration_cast<std::chrono::seconds>(std::chrono::steady_clock::now() - start_time).count(),
 #endif
-		 (unsigned long)(partition.pc.GetTotalPlayTime() + 0.5));
+		 (unsigned long)(partition.pc.GetTotalPlayTime().count() + 0.5));
 
 #ifdef ENABLE_DATABASE
 	const Database *db = partition.instance.database;

src/player/Control.hxx

@@ -231,7 +231,7 @@ class PlayerControl final : public AudioOutputClient {
 
 	const ReplayGainConfig replay_gain_config;
 
-	double total_play_time = 0;
+	FloatDuration total_play_time = FloatDuration::zero();
 
 public:
 	PlayerControl(PlayerListener &_listener,
@@ -580,7 +580,7 @@ public:
 		replay_gain_mode = _mode;
 	}
 
-	double GetTotalPlayTime() const noexcept {
+	auto GetTotalPlayTime() const noexcept {
 		return total_play_time;
 	}
 

src/player/Thread.cxx

@@ -766,7 +766,7 @@ PlayerControl::PlayChunk(DetachedSong &song, MusicChunkPtr chunk,
 	const double chunk_length(chunk->length);
 
 	outputs.Play(std::move(chunk));
-	total_play_time += chunk_length / format.GetTimeToSize();
+	total_play_time += FloatDuration(chunk_length / format.GetTimeToSize());
 }
 
 inline bool