Canvas size lock functionality doesn't handle non-integer multiples of aspect ratio cleanly

When the aspect ratio of the canvas size is locked, manually entering a new width that doesn't divide the aspect ratio cleanly then changing it back will usually leave rounding errors and a few pixels more or less.

Example:
- Set canvas size to 16:9 (eg 960x540) and lock aspect ratio
- Change height to something that doesn't divide 9 cleanly (eg 400) and set this to be the new resolution by pressing enter
- Change height back to 540, and notice how how width is now 962

I realise how this is technically correct from an implementation standpoint, but it's not very intuitive - perhaps store the original aspect ratio whenever the lock icon is enabled, and don't update it until the lock is disabled? This could enable a workflow where the only way to change aspect ratio is an explicit unlocking of the width and height, which I think is more intuitive.