Clarified behavior when activity is resized or put in fullscreen
mode, per b/28580007 . Also (per email from o-o) removed misleading
statement about when onStop() might or might not be called.
Both changes can go live now (multiwindow update applies to DP1 & 2,
and onStop() clarification applies to all versions of API), so I'll
submit as soon as this is approved.
See first comment for doc stage location.
bug: 28580007
Change-Id: Ib008f24e5796ec7810b67c91e512e679680d4afd
4d93a21980