Can't select custom image sizes

[robertaccettura]

Since upgrading to WordPress 3.5 the only image sizes in the dropdown are Thumbnail, Medium, Full. I've tried adding via add_image_size() and Additional image sizes (zui) plugin (which I've used pre 3.5 just fine). In both cases, I see the additional sizes created in the upload directory, however I'm unable to see them in the dropdown.

Given the widths are the only thing I specify due to my design, the height is variable. The only way to use the image editor and get a sized image is to ls the upload dir and find the right image, copy paste it. Or do the math to figure out what the filename would be.

Setting sev to 'major' since this is a pretty big usability problem.

[SergeyBiryukov]

Duplicate of #22911.