function onTick() {
		var b = self._benchmarks.shift();
		if ( b ) {
			b.run();
			if ( !b.ended() ) {
				return b.once( 'end', next );
			}
			return next();
		}
		self._running = false;
		self.emit( 'done' );
	}
Callback invoked upon the next tick.

@private
@returns {void}