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Currently OAuthed site is detected at the last stage of login flow when
the redirect happens with the completion request parameters. However
this site at the final step may be wrong due to multiple sites using a
common site for handling the OAuth login.

Instead this CL detects this OAuth requestor site based on the first
navigation to the OAuth provider site.

This CL also refactors a bit to pass down the entire navigation
redirect chain to the detector.

Bug: 1161451
Change-Id: I3f76c76b0f36106150b1ffa1277e129102a7e5e3
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2602078Reviewed-by: Michael Crouse <mcrouse@chromium.org>
Commit-Queue: rajendrant <rajendrant@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839186}