Remove activity leak.

mState can be used across activities on configuration changes. This is
because even though we put it into Bundle, the bundle never leaves the
process so when we take State object, it's still the old one.

Test: No more activity leak after fixing. Auto tests pass.
Bug: 62147171
Change-Id: Ie805a85a56dc5b009dd0903e094fc5b8976f6b75