Remove WeakReference from ObjectAnimator

Fixes: 212993949

ObjectAnimator was using a WeakReference for the target,
but because it is animated every frame, the WeakReference
can never be collected. This CL removes the unnecessary
WeakReference.

Test: ran existing tests
Change-Id: Id688a62d49c8f3f3c86c63dc70b576629f9f137c
1 file changed