Fix security vulneratibly 31960359

BufferQueueCore features a variable mLastQueuedSlot which is not
initialized in its constructor resulting in security vulnerability

Bug: 31960359
Change-Id: If892f59f6288d8b81b1e312995832a20c8341494
Tests: Manually on Angler
(cherry picked from commit dffa078205f6b6c17e24214928f642393423e081)
1 file changed