Wait until action taken before long screenshot is exported.

Just supporting the same actions as before for now. This will be more
important once we're honoring the crop bounds (since the export bitmap
can't be known ahead of time).

Also fix the share intent to show sharesheet.

Bug: 179175119
Bug: 179176057
Test: Validated that share and edit functionality worked and was
deferred (via logging).

Change-Id: I684a01e063b20fcf4eb61315c649769064cadf41