Steps:
1. Visit https://minorninth.github.io/aria-live-region-tests/live_region_tests.html with screen reader
2. Under the "polite" section click "set textContent" (notice "Live region succeeded" is spoken)
3. Click the same button again
"Live region succeeded" should be spoken a second time.
It currently is not, which is different from Firefox. Example of a bug it causes: In Google Docs arrow between two lines with the same text. It is not spoken, since Docs populates a live region with what ends up being the same text.
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