more consistent code path: call SoundIsFinishedPlaying when the driver stops mixing, even if it's due to RageSoundDriver::StopMixing

stepmania/src/RageSound.cpp

@@ -335,26 +335,8 @@ void RageSound::StopPlaying()
 	if( !m_bPlaying )
 		return;
 
-	m_iStoppedSourceFrame = (int) GetPositionSecondsInternal();
-
 	/* Tell the sound driver to stop mixing this sound. */
 	SOUNDMAN->StopMixing(this);
-
-	/* Lock the mutex after calling UnregisterPlayingSound.  We must not make driver
-	 * calls with our mutex locked (driver mutex < sound mutex).  Nobody else will
-	 * see our sound as not playing until we set playing = false. */
-	m_Mutex.Lock();
-
-//	LOG->Trace("set playing false for %p (StopPlaying) (%s)", this, this->GetLoadedFilePath().c_str());
-	m_bPlaying = false;
-	
-	m_iMaxDriverFrame = 0;
-	m_HardwareToStreamMap.Clear();
-	m_StreamToSourceMap.Clear();
-
-//	LOG->Trace("StopPlaying %p finished (%s)", this, this->GetLoadedFilePath().c_str());
-
-	m_Mutex.Unlock();
 }
 
 /* This is similar to StopPlaying, except it's called by sound drivers when we're done