Check status of <link rel=serviceworker>

[sideshowbarker]

The <link rel=serviceworker> link type needs to be defined, along with the associated scope, workertype, and usecache content attributes, and the corresponding scope, workerType, and useCache IDL attributes need to be added to the HTMLLinkElement interface definition.

whatwg/html@c5d4f5c

[travisleithead]

Wait for #822's PR #852 before starting this--the refactoring will put this in the right spot and be easier to merge.

[travisleithead]

Checked with our Service Worker team, and learned that this feature is not yet deployed generally in Chrome (origin trial only: https://www.chromestatus.com/features/5682681044008960), and is not supported in any other UA at the moment. Given this status, it would be inappropriate to land this feature in HTML for 5.2. We should consider adopting this in once it's available for testing publicly, perhaps in the 5.3 timeframe.

Dropped "match reality better" as this isn't true, and dropped high-priority, as this doesn't seem to apply to future HTML5 milestones.

[chaals]

This should be checked again in time to get it in for wide review if there is uptake.

[patricia-gallardo]

@travisleithead postponed intake last year waiting on other UAs - however Chrome seems also to have dropped this as of March 2018 : https://www.chromestatus.com/features/5682681044008960

"Add support for LINK rel=serviceworker as an element and header to allow the installation of Service Worker declarative in a document or via a header.
Update (2018-03-26): This was removed from the specification and is no longer being pursued."

Therefore closing the issue.