GitLab

NOTE: There are still unresolved A11y issues. The current A11y follows
the same rules for the chrome browser search input. See
https://drive.google.com/file/d/1aXwE_2OJb6uMqhiyKLFOCyQ_c0sqrLxM/view

* Hides old search UI and shows new search UI when flag is on.
* Produces a list of random results when user inputs into search bar.
* Basic stylization to account for when screen is narrow mode.
* JS handling for keyboard and mouse events, highlighting correct row.
* Temporary stylizations and functions for testing.
* Rows are not actionable yet but are forced to via tabindex.
* Modified os settings ui and os toolbar so that the old search UI is
  not impacted but provides permissive environment for new UI.
* Tests.

Screenshots:
* Regular (wide) mode: https://screenshot.googleplex.com/9zZVYXoOzzQ
* Narrow mode: https://screenshot.googleplex.com/tpR1jMg0Cjv
* Narrow mode (not showing search):
  https://screenshot.googleplex.com/Labxcscu47U

Bug: 1056909
Change-Id: I5d8ae7313cfb799ead69dad6ffb06f4c4bcc4f8c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2099468Reviewed-by: dpapad <dpapad@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Reviewed-by: jimmy gong <jimmyxgong@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#753786}