function initPipeline() {
    if (pipeline) pipeline.destroy();
    pipeline = new Pipeline();
    debug = {pipeline};
    updatePipelineSourceIfSet();
    updatePipelineTransform();
    updatePipelineSink();
    console.log(
        '[initPipeline] Created new Pipeline.', 'debug.pipeline =', pipeline);
  }
Initializes/reinitializes the pipeline. Called on page load and after the
user chooses to stop the video source.