Bug1087494-[Gallery]-Update Image Edit Crop Flow

I think I understand what you're doing here, but I don't understand the comment.  It would also be okay here to simplify and just always call resetPreview on the assumption that 95% of the time it will be necessary to do that.

I had imagined that you would implement this by keeping two different previews: one full one for the crop screen and another cropped one for the other edit views. I see that you are instead just keeping one and switching back and forth. That's a simpler approach and probably just as efficient or even more efficient.  I would like comments that have a little more detail expaining what is going on, however.