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 - aria-label, aria-pressed, role="button" should all be on the same element. This will avoid vocalizing 'group' and will have a correct order of strings, e.g. label, selected, toggle button
 - always have aria-pressed and default to false, so that buttons are always considered toggle buttons, otherwise it will be just a button before selection and toggle button after the selection.

Bug: 992059
Change-Id: I16de081e5f3b65b5ea13a25e54234a48dc6f602c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1745047Reviewed-by: Kyle Milka <kmilka@chromium.org>
Commit-Queue: Gayane Petrosyan <gayane@chromium.org>
Cr-Commit-Position: refs/heads/master@{#685440}