Refactored Android samples / embedder.

samples/android_sample/jni/sound_service.h

 #ifndef SOUND_SERVICE_H
 #define SOUND_SERVICE_H
 
 #include <android_native_app_glue.h>
 #include <SLES/OpenSLES.h>
 #include <SLES/OpenSLES_Android.h>
 #include <SLES/OpenSLES_AndroidConfiguration.h>
 #include "jni/types.h"
 
 class SoundService {
   public:
     explicit SoundService(android_app* application);
     int32_t Start();
     void Stop();
 
     int32_t PlayBackground(const char* path);
     void StopBackground();
 
   private:
     android_app* application_;
     SLObjectItf engine_;
     SLEngineItf engine_if_;
     SLObjectItf output_mix_;
     SLObjectItf background_player_;
     SLPlayItf background_player_if_;
     SLSeekItf background_player_seek_if_;
 };
 
-int32_t PlayBackground(const char* path);
+void PlayBackground(const char* path);
 void StopBackground();
 #endif
-