Correctly update full size in MediaSizeWidget

Change the event calls to 'choose' instead of 'select' to make sure
they are triggered selectively; also, change the order of updating
the scalable and the UI when full size button is clicked to make
sure the size is stored and displayed correctly.

Change-Id: Ie224d40b56f848bccb13f3f6d15fe30ac41fc050
(cherry picked from commit 981d86f06a9b68f6ced7e5c3c1a69d059190e755)