export: fixed audio exporting with new renderer system

app/task/export/export.h

@@ -43,6 +43,8 @@ protected:
 
   virtual void FrameDownloaded(const QByteArray& hash, const QLinkedList<rational>& times) override;
 
+  virtual void AudioDownloaded(const TimeRange& range, SampleBufferPtr samples) override;
+
 private:
   QHash<QByteArray, FramePtr> rendered_frame_;
 
@@ -60,6 +62,8 @@ private:
 
   int64_t frame_time_;
 
+  AudioPlaybackCache audio_data_;
+
 };
 
 OLIVE_NAMESPACE_EXIT