Work around polymer issue in hide-show.
Work around polymer issue in hide-show.

samthor/web-animations-demos,robcolburn/web-animations-demos,robcolburn/web-animations-demos,web-animations/web-animations-demos,samthor/web-animations-demos,samthor/web-animations-demos,web-animations/web-animations-demos,web-animations/web-animations-demos,robcolburn/web-animations-demos