message: videoio(gstreamer): support dumping of VideoWriter pipeline
diff: @@ -1657,6 +1657,8 @@ bool CvVideoWriter_GStreamer::open( const char * filename, int fourcc,
  }
  #endif
  + GST_DEBUG_BIN_TO_DOT_FILE(GST_BIN(pipeline), GST_DEBUG_GRAPH_SHOW_ALL, "write-pipeline");
  +
  stateret = gst_element_set_state(GST_ELEMENT(pipeline), GST_STATE_PLAYING);
  if(stateret == GST_STATE_CHANGE_FAILURE) {
  handleMessage(pipeline);
  