Support the section role in ChromeVox

https://chromium-review.googlesource.com/c/chromium/src/+/1779430

introduced the section role, which is essentially just a region.
In particular, we want to honor its announcements when landing on one of their descendants (an output rule's enter rule); get this by making it inherit from abstractContainer.

R=dmazzoni@chromium.org

Fixed: 1075615
Change-Id: I920346c2423f1b24e300456ce585421a385776e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2168513
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#763546}

chrome/browser/resources/chromeos/accessibility/chromevox/background/output.js

@@ -2274,6 +2274,7 @@ Output.ROLE_INFO_ = {
   row: {msgId: 'role_row', inherits: 'abstractContainer'},
   rowHeader: {msgId: 'role_rowheader', inherits: 'cell'},
   scrollBar: {msgId: 'role_scrollbar', inherits: 'abstractRange'},
+  section: {msgId: 'role_region', inherits: 'abstractContainer'},
   search: {msgId: 'role_search', inherits: 'abstractContainer'},
   separator: {msgId: 'role_separator', inherits: 'abstractContainer'},
   slider: {msgId: 'role_slider', inherits: 'abstractRange', earconId: 'SLIDER'},