Check class type before creating animator

ag/17048689 removed the check for the drawable type before creating the
NumPadAnimator. A check for a GradientDrawable should be re-introduced
for when it is not that type (such as on AAOS).

Bug: 223386100
Test: manual
Change-Id: I247a6731e6e633f1a13e3acd9fe7ac81d474e126