Return the actual interpolator of the ViewPropertyAnimator

The implementation of getInterpolator() was always returning null
(probably a quick copy-paste from the default Animator implementation).
This patch fixes the problem by returning the interpolator set by
setInterpolator(TimeInterpolator) or the default one if none has been
set yet.

This patch also avoid creating multiple instances of ValueAnimator in
order to retrieve some default values.

Change-Id: I8880f419f021a8b980fb32bebe927915fde19bf7
remove dependency if airplane mode is not set

Change-Id: I8c01b4ac9cea8271b4a8140b24cfa56280435448
Copy/paste text in gtalk

Change-Id: I9fe3634dfdc64cb37ece7f431d12845c164d639b