Compress scripts/styles: 3.5.1-alpha-23280.
Try not to send Last-Modified, even with an empty value. Some servers interpret an empty value as the epoch.

Props nacin, slene, SergeyBiryukov, andy
fixes #23021 for 3.5
Media: Pass thumbnail and medium sizes to image_constrain_size_for_editor() to force constraints based on the current DB options for those sizes. History: see #22598, #22738.

props jond3r
fixes #23102
for 3.5
Don't unnecessarily re-render the attachment details view when editing the title and caption. Re-rendering causes issues with tabbing and focus, and is only necessary for other views (such as "Caption this image..." when editing a gallery).

Merges [23283] to the 3.5 branch.

props koopersmith.
fixes #23054.