Fix when >2 keyframes supplied

When there are more than two keyframes, we treat each keyframe
interval as its own separate period during which to calculate animated
values. To do this, we calculate an intervaleFraction from the overall
elapsed fraction of the entire animation. This intervalFraction is then
used to calculate the animated values in that interval.

However, we failed to actually use the intervalFraction in some code
paths, using the overall fraction instead. This caused a jumping behavior
because we were incorrectly calculating the values during the intervals.

Change-Id: Ia052e1e8b5130ff450ee20c0a3581e3de42399e1