We've moved getCroppedRegionBlob() out of ImageEditor. Now we get the crop region here, using cropResizeRotate.  We used it before to rotate the preview image displayed by the image editor.  Now we're using it to actually crop (and possibly downsample) the full-size image.

The new code here computes the arguments that we're going to pass to cropResizeRotate().  First, we make sure the output type is valid.