The intrinisic duration of an empty par group should be zero
The intrinisic duration of an empty par group should be zero

See
https://dvcs.w3.org/hg/FXTF/raw-file/tip/web-anim/index.html#the-intrinsic-duration-of-a-parallel-animation-group

Currently, the intrinisic duration of an empty par group is -Infinity, because
that is the value of Math.max.apply([]).

beni55/web-animations-js-legacy,web-animations/web-animations-js-legacy,birtles/web-animations-js,dstockwell/web-animations-js,web-animations/web-animations-js-legacy,beni55/web-animations-js-legacy,birtles/web-animations-js,web-animations/web-animations-js-legacy,beni55/web-animations-js-legacy,beni55/web-animations-js-legacy,birtles/web-animations-js,dstockwell/web-animations-js