VIRO-888: iOS video crashes
VIRO-888: iOS video crashes

We were updating the surface when width or
height was changed, without first checking if
a source was checked. Changed this class to
be more inline with what we're doing with images
and OBJ, where we load the video on
didSetProps.


Former-commit-id: c68e399c473a9b2194807bcdd758e0deb308735c
viromedia/viro,viromedia/viro,viromedia/viro,viromedia/viro