Jun, can you provide some context and elaborate what you expect to be done with this issue? The test obviously does not control this directly, and generally tests the different layer, so I'm not quite sure how I can help here.

I think the original description needs to be updated, here it is:

The context:
https://chromium-review.googlesource.com/c/chromium/src/+/1015742/8/third_party/WebKit/LayoutTests/flag-specific/enable-features%253DNetworkService/http/tests/inspector-protocol/network/xhr-interception-auth-fail-expected.txt#11

When running the browser test:
//third_party/blink/web_tests/http/tests/inspector-protocol/network/xhr-interception-auth-fail.js
The |resource_request->do_not_prompt_for_login| is set to true at:
https://cs.chromium.org/chromium/src/content/renderer/loader/web_url_loader_impl.cc?rcl=2995cf7bcf7db1e0ff5177aedf972414f4f8f523&l=720

And I remember it is because the |gurl.has_username()| is true:
https://cs.chromium.org/chromium/src/content/renderer/loader/web_url_loader_impl.cc?rcl=97e6cbbcb0071b5db924187dd6bb1ea4de129f96&l=719
since the test uses a bogus user:
https://cs.chromium.org/chromium/src/third_party/blink/web_tests/http/tests/inspector-protocol/network/resources/xhr-iframe-auth-fail.html?rcl=97e6cbbcb0071b5db924187dd6bb1ea4de129f96&l=10

I remember we had some discussion about the above test data and concluded that maybe the above test data needs to be updated?