GitLab

Some details:
- Suggestions/settings link will be highlighted when using down/up to
navigate
- Tab/Right no longer commits suggestions.
- If user keeps typing after a suggestion is highlighted, we cancel the
highlight.

Test: add unit test and tested with Chrome on Linux
Bug: 1099498
Change-Id: If890b9d39fa86e55398841c2a8038922d59488f6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2269157Reviewed-by: Keith Lee <keithlee@chromium.org>
Reviewed-by: Darren Shen <shend@chromium.org>
Commit-Queue: Jing Wang <jiwan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786130}