@zcbenz Nice find narrowing down the issue, an alternative approach below.

https://github.com/electron/electron/blob/master/patches/chromium/delay_lock_the_protocol_scheme_registry.patch should let us register schemes on the browser process from registerSchemesAsPrivileged . But didn't realize there was no url_util call for registering service worker schemes and savable schemes so effectively we were only registering it on network and renderer process https://source.chromium.org/chromium/chromium/src/+/master:content/common/url_schemes.cc;l=112-118.

So we can add a method url::AddServiceWorkerScheme that would allow us to register the scheme from browser process via the registerSchemesAsPrivileged method and we can keep the condition in AddAdditionalSchemes to only handle network process, this way we don't have to use the testing api.

@deepak1556 Thanks for the insights on this issue, I have changed the code to add service worker scheme directly instead of full re-registration.

Release Notes Persisted

Fix service worker not working with custom protocol.

I was unable to backport this PR to "10-x-y" cleanly;
you will need to perform this backport manually.

I have automatically backported this PR to "11-x-y", please check out #28353

I have automatically backported this PR to "13-x-y", please check out #28354

I have automatically backported this PR to "12-x-y", please check out #28355