The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/466d795b90b790a9ade7ea407639202b67456b29

commit 466d795b90b790a9ade7ea407639202b67456b29
Author: Elly Fong-Jones <ellyjones@chromium.org>
Date: Wed Jan 17 17:33:47 2018

cocoa: expose keyword hints in omnibox to a11y

This change:
1) Hides the keyword hint and selected keyword hint buttons from VoiceOver;
2) Augments the location bar's description with hint text when those buttons
   are visible

The end result is this:
1) User types "foo": omnibox reads as now
2) User types "google" and the omnibox offers a tab completion:
    Before this CL: "google, contents selected, edit text"
    After: "google, contents selected, press Tab to search google, edit text"
3) User hits tab after (2):
    Before: "google, contents selected, edit text"
    After: "Search Google, edit text"

This helps indicate the actual state of the omnibox. Another option would be to
make the buttons accessibility-visible, but then the user has to know to
navigate to them to find out the omnibox state.

Bug:  752592 
Change-Id: I593f05dd2dce1276eb4aada6c17755b711e7bf6e
Reviewed-on: https://chromium-review.googlesource.com/865655
Reviewed-by: Sidney San Martín <sdy@chromium.org>
Commit-Queue: Elly Fong-Jones <ellyjones@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529790}
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/keyword_hint_decoration.h
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/keyword_hint_decoration.mm
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/location_bar_decoration.h
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/location_bar_decoration.mm
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/location_bar_view_mac.mm
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/selected_keyword_decoration.h
[modify] https://crrev.com/466d795b90b790a9ade7ea407639202b67456b29/chrome/browser/ui/cocoa/location_bar/selected_keyword_decoration.mm