Improve AXRelationCache support for element reference properties.
Element Reference properties, like el.ariaLabelledByElements, can be set at any time, including when the elements referred to by the properties are not yet in the document, or not yet in a valid scope.
This change ensures that when elements become valid targets for the Element Reference properties, the host element is updated appropriately and, where relevant, the appropriate events are fired.
Change-Id: Ic20559da184b3547803de566106dd03ce2bea981
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5969976
Commit-Queue: Aaron Leventhal aleventhal@chromium.org
Reviewed-by: Aaron Leventhal aleventhal@chromium.org
Reviewed-by: Vladimir Levin vmpstr@chromium.org
Cr-Commit-Position: refs/heads/main@{#1384316}