Reduce the size of the test it was too big for my macbook

macbook with retina display by default can only show up to a
690 pixel tall window because it does pixel doubling by default and
it has a title bar. 1400 - title bar / 2 is < 700.

Also a minor fix to release texture resources more quickly on
the imageslicemapper.

Change-Id: I6421807cbb3e7bd048c333909c18f6a95d21d662
Merge topic 'fit_test_to_macbook' into master

03efc593 Reduce the size of the test it was too big for my macbook