code: function onload() {
  	debug( 'proxy <iframe> "load" event' );
  	loaded = true;
  
  	// flush any buffered API calls
  	if ( buffered ) {
  		for ( let i = 0; i < buffered.length; i++ ) {
  			submitRequest( buffered[ i ] );
  		}
  		buffered = null;
  	}
  }
docs: The proxy <iframe> instance's "load" event callback function.
  
  @api private