decoder/Thread: move code to DecoderControl::LockIsReplayGainEnabled()

src/decoder/Control.hxx

@@ -257,6 +257,12 @@ public:
 		return HasFailed();
 	}
 
+	[[gnu::pure]]
+	bool LockIsReplayGainEnabled() const noexcept {
+		const std::scoped_lock<Mutex> protect(mutex);
+		return replay_gain_mode != ReplayGainMode::OFF;
+	}
+
 	/**
 	 * Transition this obejct from DecoderState::START to
 	 * DecoderState::DECODE.

src/decoder/Thread.cxx

@@ -261,12 +261,9 @@ LoadReplayGain(DecoderClient &client, InputStream &is)
 static void
 MaybeLoadReplayGain(DecoderBridge &bridge, InputStream &is)
 {
-	{
-		const std::scoped_lock<Mutex> protect(bridge.dc.mutex);
-		if (bridge.dc.replay_gain_mode == ReplayGainMode::OFF)
+	if (!bridge.dc.LockIsReplayGainEnabled())
 		/* ReplayGain is disabled */
 		return;
-	}
 
 	LoadReplayGain(bridge, is);
 }