Make "done" phase of ScreenPinningTestActivity reentrant.

In the original code, in mDone.run() moves the index
forward so it is not reentrant, unlike other
phases.
With this change, it is reentrant.

(cherry-picked from d39d155b818cc612b8ac73d550521b173c8e7375)

Change-Id: Iab03f4cc08a4025b111c402c74739cbd90f137bf
1 file changed