[iOS]Test that signin is offered in the top of feed’s signin promo

This CL does two related changes.

Firstly, it add a test that shows that the fact that signin is offered
at the top of the feed if and only if the user interacted
with the feed.
I thought it was not logged; but I missed the log in the view
controller.
Logs are normally done in the mediator. However, I don’t intend to
rewrite code that works correctly. And this ensure that we only log it
when the promo appear, and not when the mediator request to display
the promo while the promo already exists.

Secondly, it slightly cleans-up feed_top_section_mediator.mm.
The removed comment was essentially restating (wrongly) what was
done in the code below. The removed variable name was misleading.
And `if(X) {return true;}return false;` should have been a
simpler `return X`.

Bug: 41493423
Change-Id: I5f318850fe3ec330de1a6a6c762b1c1cc9c94b65
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6218485
Reviewed-by: Adam Arcaro <adamta@google.com>
Commit-Queue: Arthur Milchior <arthurmilchior@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1417333}
NOKEYCHECK=True
GitOrigin-RevId: 0b82c896712a17dd63b5c779a1131d1c437709f2
3 files changed
tree: 860e1a7dba9d49b40d8a59100cd91a75fb2090ed
  1. build/
  2. chrome/
  3. components/
  4. google_internal/
  5. intents/
  6. net/
  7. public/
  8. testing/
  9. third_party/
  10. tools/
  11. web/
  12. web_view/
  13. .swift-format
  14. BUILD.gn
  15. COMMON_METADATA
  16. DEPS
  17. DIR_METADATA
  18. features.gni
  19. OWNERS
  20. PRESUBMIT.py
  21. PRESUBMIT_test.py
  22. README.md
README.md

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