Not a developer by any means but I followed the rabbit hole towards this topic with the 'Block cross-origin <a download>' change essentially killing a feature(for now) on a extension I use quite a bit. https://github.com/extesy/hoverzoom/issues/344

The ease at which you can save a image by hovering over a image and hitting 'S' without a contextual download window popping up was an oddly nice QoL feature. If an API can help aid in something like that I am all for it while trying to minimize the 'user-mediated cross-origin information leakage' issue.

Additionally, while slightly off topic, is there a command line flag for disabling that feature of blink? I am not quite sure what I am to look for in the settings.json5 for the setting name. This is assuming '--blink-settings <name>[=<value]' could be applied to it.

Kind regards to all of the work put in still.

I think we're building this out through the new background fetch JS API?  Although I don't think that lets us give the file contents as they are downloaded (we still do blobs on a per-file basis).

+peter@ to help figure out if that meets your needs and/or if it'd be worth tweaking the spec to address it.  :).

Yeah, that sounds like Background Fetch:
https://wicg.github.io/background-fetch/

Support for accessing in-progress downloads is in the specification as BackgroundFetchRegistration.activeFetches. It's something we eventually want to support as there are very good use-cases, but it's currently scoped post v1.