[w3c/ServiceWorker] Fix less fragile |fetchController| termination check (PR #1779)

This is a follow up of https://github.com/w3c/ServiceWorker/pull/1777#discussion_r2141544666.
https://infra.spec.whatwg.org/#abort-when adds the check each time the step is executed.  However, there is only a step between and the abort-when and if-aborted, it should be less effective abort than we expect.  Let me steps to avoid that.


<!--
    This comment and the below content is programmatically generated.
    You may add a comma-separated list of anchors you'd like a
    direct link to below (e.g. #idl-serializers, #idl-sequence):

    Don't remove this comment or modify anything below this line.
    If you don't want a preview generated for this pull request,
    just replace the whole of this comment's content by "no preview"
    and remove what's below.
-->
***
<a href="https://pr-preview.s3.amazonaws.com/yoshisatoyanagisawa/ServiceWorker/pull/1779.html" title="Last updated on Jun 12, 2025, 8:02 AM UTC (7357cbf)">Preview</a> | <a href="https://pr-preview.s3.amazonaws.com/w3c/ServiceWorker/1779/ef029c5...yoshisatoyanagisawa:7357cbf.html" title="Last updated on Jun 12, 2025, 8:02 AM UTC (7357cbf)">Diff</a>
You can view, comment on, or merge this pull request online at:

  https://github.com/w3c/ServiceWorker/pull/1779

-- Commit Summary --

  * More easy to abort

-- File Changes --

    M docs/index.bs (4)

-- Patch Links --

https://github.com/w3c/ServiceWorker/pull/1779.patch
https://github.com/w3c/ServiceWorker/pull/1779.diff

-- 
Reply to this email directly or view it on GitHub:
https://github.com/w3c/ServiceWorker/pull/1779
You are receiving this because you are subscribed to this thread.

Message ID: <w3c/ServiceWorker/pull/1779@github.com>