Defines a means for site developers to programmatically give the User Agent hints on the download priority of a resource.
christian oliff commented
Maybe this feature request could be renamed to match the new proposed solution for this:
It's coming to Chrome Canary soon and I think it'd be a great feature to have.
This is one of the most important and useful of features listed on status.modern.ie. In particular, the postpone attribute would obviate much of the need for performance-intensive scrolling-based lazy loading functionality in JS.