LiveAnnouncer should have a global duration to remove the text

[jasonzhang2022]

Please describe the feature you would like to request.

1. set a global duration,
2. LiveAnnouncer.annouce(text)
3. the text is removed from DOM after global duration.

What is the use-case or motivation for this proposal?

When I open a MatDialog, I use screen reader(Voice Over) VO plus left arrow to do linear navigation. When I come to the beginning of dialog, I shouldn't be able to navigate to anywhere. However, I navigated to the DOM for LiveAnnouncer if LiveAnnoucer is used once.

I can use announce(text, duration) to work around this. This requires a duration for every announce call.

Is there anything else we should know?

[jasonzhang2022]

Please add a Google label. I reported this as Googler

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