The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9dc28a9ede044f6a7504b164d1a7f9da33780640

commit 9dc28a9ede044f6a7504b164d1a7f9da33780640
Author: Aaron Leventhal <aleventhal@chromium.org>
Date: Fri Jan 12 02:26:53 2018

Omnibox accessibility: expose accessibility semantics for suggestion list

We currently use value changes to announce friendly suggestions in the omnibox popup as they are selected. This is the most practical thing to do as the omnibox is in a different window, and keyboard input needs to go to the textbox.

This CL expands on the value change approach by exposing the suggestion list box with proper semantics:
- Text field has "controller for" relationship to popup list
- Popup list is exposed with list box role, children having the listbox option role
- Options have appropriate states such as selectable, and the friendly name
- Fire "selected" event on options

This is similar to how UIA is handling autocomplete lists, so that focus doesn't switch back and forth between the text field and the list.
The assistive technology (e.g. screen reader) can choose to announce text of option with selected event of controlled list box, or to value change events on the text box.

Bug:  787860 
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: Ibef0b8d0a48baf05702ebcdddb72e258ed82413f
Reviewed-on: https://chromium-review.googlesource.com/817693
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#528853}
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.cc
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_result_view.cc
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_result_view.h
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_result_view_unittest.cc
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_view_views.cc
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/chrome/browser/ui/views/omnibox/omnibox_view_views.h
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/components/omnibox/browser/autocomplete_match_type.cc
[modify] https://crrev.com/9dc28a9ede044f6a7504b164d1a7f9da33780640/components/omnibox/browser/autocomplete_match_type.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6c1002a18834709ed10e52dfb19bf98608b77336

commit 6c1002a18834709ed10e52dfb19bf98608b77336
Author: Aaron Leventhal <aleventhal@chromium.org>
Date: Tue Jan 16 18:44:27 2018

Omnibox semantics CL polish post landing follow up

Bug:  787860 
Change-Id: I5560aec038598ffea091eca21e0965eb640b8cc9
Reviewed-on: https://chromium-review.googlesource.com/864304
Reviewed-by: Trent Apted <tapted@chromium.org>
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#529471}
[modify] https://crrev.com/6c1002a18834709ed10e52dfb19bf98608b77336/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.h
[modify] https://crrev.com/6c1002a18834709ed10e52dfb19bf98608b77336/chrome/browser/ui/views/omnibox/omnibox_result_view.cc
[modify] https://crrev.com/6c1002a18834709ed10e52dfb19bf98608b77336/chrome/browser/ui/views/omnibox/omnibox_result_view.h
[modify] https://crrev.com/6c1002a18834709ed10e52dfb19bf98608b77336/chrome/browser/ui/views/omnibox/omnibox_view_views.cc
[modify] https://crrev.com/6c1002a18834709ed10e52dfb19bf98608b77336/components/omnibox/browser/autocomplete_match_type.cc

Reopening for some small tweaks:
- Popup should have COLLAPSED/EXPANDED states.
- State change for above state.
- Selection event should occur even for the first item when popup opens automatically. For example, go to location bar with Ctrl+L, type a letter -- there should be a selection event.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a

commit 93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a
Author: Aaron Leventhal <aleventhal@chromium.org>
Date: Mon Jan 22 17:11:48 2018

Refine Omnibox accessibility semantics

- Popup should have COLLAPSED/EXPANDED states.
- State change for above state.
- Selection event should occur even for the first item when popup opens automatically.
  For example, go to location bar with Ctrl+L, type a letter. As the popup opens it also
  needs to fire a selection event for the first item.

Bug:  787860 
Change-Id: Ie5efac8d264ef3384453bed0694b274997c46b7c
Reviewed-on: https://chromium-review.googlesource.com/871472
Reviewed-by: Justin Donnelly <jdonnelly@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#530898}
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/chrome/browser/ui/views/omnibox/omnibox_popup_contents_view.cc
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/chrome/browser/ui/views/omnibox/omnibox_result_view_unittest.cc
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/chrome/browser/ui/views/omnibox/omnibox_view_views.h
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/chrome/browser/ui/views/omnibox/omnibox_view_views_browsertest.cc
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/components/omnibox/browser/autocomplete_controller.h
[modify] https://crrev.com/93d7d29ba3db93ffa68e4dd91e2a3b8d611a4b2a/ui/accessibility/platform/ax_platform_node_win.cc