SUMMARY
Using Image -> Scale Image to a New Size... doesn't scale transform masks properly, resulting in the scaled up/down image looking different form the original image.

In particular, the position of a transform mask isn't scaled.

STEPS TO REPRODUCE
1. Create a new image with 200px x 100px size.
2. Draw something on the left side.
3. Add a transform mask to the layer and select it.
4. Select the transform tool and move the mask so that the drawing ends up in the right side of the canvas.
5. Click image -> scale image to new size, set the size 100px x 50px, and click OK.

OBSERVED RESULT

The canvas is now blank. The drawing disappears.

EXPECTED RESULT

The drawing should be on the right side of the scaled down image, just like it was on the right side in the original image.

ADDITIONAL INFORMATION

In the original image with 200px of width, the left side ranged from 0px to 100px, and the right side 100px to 200px in the horizontal axis. The drawing was in the 0-100px range, the left side. We moved it to the 100-200px range, the right side. When the image was scaled down to 100px width, the position of the transform remained in the 100-200px range, which is now OUTSIDE of the canvas, hence why it disappeared (if we scaled up to 1000px, it would end up in the left side instead). That is, the position wasn't scaled at all. The expected result would have been for it to be scaled down to the 25-50px range.

The current behavior is what you'd expect from Resize Canvas, not from Scale Image to New Size.