[web-animations-1] Add parameter to getAnimations for getting animations in descendants too #2058
Description
From @birtles on March 17, 2016 0:48
As discussed and minuted here: The ideas we came up with are here: https://docs.google.com/document/d/1lQbgJ0fZYGn1_qboj59G-MOILK33z4kmBdjgtSHF2gA/edit#heading=h.cioj28lsgoa2
A more concrete elaboration on that proposal is described here:
https://bugzilla.mozilla.org/show_bug.cgi?id=1254761#c0
Copied from original issue: w3c/web-animations#146