Fix potential divide by 0 in WebVideoTranscode::getMaxSizeTransform

If the method got called for an audio file (It was being called
on .wav files, at least locally), it would divide by 0. Add a
check to see if height === 0 before trying to divide by
height.

Change-Id: Id1b5872d741208338cd7157f83f4ff6762ae34ee
Merge "Fix potential divide by 0 in WebVideoTranscode::getMaxSizeTransform"