Fix video capture intent preview alert for effects. DO NOT MERGE.

In effects mode, stopping video record is asynchronous, and dealing
with alerts and thumbnails has to be deferred until a done callback
from the effectsrecorder.

Cherry-pick from MR1 branch to fix 5567363

Bug: 5494625
Bug: 5567363
Change-Id: I20f59c94c97425267afb10f2acaad034e01ecae5
1 file changed