[csswg-drafts] [css-animations-1] Reverse the timer when we reverse the animation during playtime

hunboy has just created a new issue for 
https://github.com/w3c/csswg-drafts:

== [css-animations-1] Reverse the timer when we reverse the animation 
during playtime ==
https://www.w3.org/TR/css3-animations/

Currently when we reverse an animation during populationtime, the 
timer is not reversed. I say timer is X. But should be 1-X

For the issure I prepared a testcase: 
https://jsfiddle.net/utasir/sup4hh90/

Press (and keep pressed) the **<** and the **>** icons for moving the 
animation, whilst this is paused currently.
For the **forward** it works as expected, but for the **backward** - 
when we reverse the animation - the timer is still X instead of 1-X

Same testcase with 1 image only for a more visible issue: 
https://jsfiddle.net/utasir/sup4hh90/1/
The image jumps, when we press the backward icon. The reason is: the 
timer is not reversed.

Issues:
 - animation-delay also could be "reversed"

mozbugzilla link: https://bugzilla.mozilla.org/show_bug.cgi?id=1247604




Please view or discuss this issue at 
https://github.com/w3c/csswg-drafts/issues/979 using your GitHub 
account