commit af67165d4a6e15ae65613f97a941d4470aacf4eb
author Aaron Leventhal <aleventhal@google.com> Fri Dec 02 23:52:41 2022
committer Chromium LUCI CQ <chromium-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Dec 02 23:52:41 2022
tree 221594d2e5ec1ae0578064789f27f6d63b9e4894
parent 40a4bee53f39ab76e29422071ea1e6fe1bb11ce7

Correct and optimize node removal and live region support

Improvements:
- AXLiveRegionTracker is actually not necessary at all.
- AXEventGenerator does not need to process every node removal, only subtree removals. This should be a big performance win when large subtrees are removed. For example, when a user navigates to a new chat or slide, and a subtree is removed with thousands of nodes. Previously, we had to walk the ancestors of every node, and we did it twice. Now, we only have to process one node in the subtree, and usually will only need to walk ancestors once (for the textfield value change check).
- Live region changes of any kind don't need to be processed where there is no kContainerLiveStatus. This saves yet more ancestor walking for DOM changes.
- Live region removals should not get events or announcements unless kContainerLiveRelevant includes a token of "all" or "removals" -- this is a correction in behavior as well as an optimization.

Test changes:
- A unit test has to change that contained an unrealistic scenario
in which node_id_to_clear should generate a live region event.
However, node_id_to_clear is only used in extremely rare
circumstances. In web content, it is used for tree resets which
should only occur when there is a serialization error.
- Unit tests for node removals in live regions were changed to set aria-relevant properties. New tests were added to try various values of aria-relevant.

Bug: none
Cq-Include-Trybots: luci.chromium.try:linux-blink-web-tests-force-accessibility-rel
Change-Id: Ifac76dd51dadfa6609f1547976004695c987d10a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4060618
Commit-Queue: Aaron Leventhal <aleventhal@chromium.org>
Reviewed-by: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1078835}