Installation detection from a web app url opened in a browser tab

[dmurph]

Standardize a way for a web app loaded in a browser tab (e.g. site.com/app) to detect if it has been installed by the user as an app.

This likely would pull over the existing WICG spec for getInstalledRelatedApps(), which includes a bunch of protections as well as features to know if a site's native app is installed or not. (explainer, MDN)

If this is something that is supported by enough vendors, then it should be in the spec. If not, we should remove it from the CR list.

This is a fork from the discussion in issue #1092 .

[dmurph]

Privacy-wise:

• The UA could report this connection after install by default (which the site can also know via server etc)
• If the user clears cookies, the UA COULD stop reporting the app is installed to protect privacy etc.
• Then, when the user launches that app the next time, the UA can resume reporting to the browser tab that it is installed - which is the same as the server knowing this again.

[marcoscaceres]

This would have privacy issues, as it would reveal what the user has installed.