add clarification for focus response

- Focus response should be always sent when there is a
  focus request.
- Otherwise, focus request will time-out and will
  leads into focus reset.

bug: 27874358
Change-Id: I9e55d0183e9b0623871103107f2e7a475d4808c3
(cherry picked from commit 972dbb9e4ff75380bac35a8f24d1a013f6290184)
1 file changed