Gecko's timing function (nsTimingFunction) needs to be specified
each control points if timing function can be represented as cubic-bezier
function. To avoid scattering control points values (e.g. 0.25, 0.1, ...)
we convert specified value to computed value and then use control points
values of the computed value.
Now animation-timing-function in keyframe is stored as specified
TransitionTimingFunction. We need a way to convert it to nsTimingFunction too.
MozReview-Commit-ID: C8j5PmJFm2i
