Fix AccessibilityInfo.announceForAccessibility not working in playground-win32 solution

[lyahdav]

Per #7290 these changes are required. I confirmed that the Playground-win32 announceForAccessibility example now works with this change.

Microsoft Reviewers: Open in CodeFlow

[asklar]

this should not be needed if you do the first API call. This is a fallback in cases where you don't have an accessible root. Narrator may not behave "as well" when setting landmark type this way, so prefer using just the xaml root.

[lyahdav]

I verified this is needed (or maybe I'm missing something about your comment?). If I delete this then Narrator doesn't announce anything when trying the AccessibilityInfo example in playground-win32 RNTester. This also aligns with what's mentioned in #7290:

AccessibleXamlRoots must be able to create an automation peer or need to set AutomationProperties::LandmarkTypeProperty() to 80002.

[asklar]

@lyahdav what is the concrete type of the thing that you pass to SetAccessibleXamlRoot ? it needs to be one of the FrameworkElement derived types that is associated with the list of derived types in this page:

https://docs.microsoft.com/en-us/uwp/api/Windows.UI.Xaml.Automation.Peers.FrameworkElementAutomationPeer?view=winrt-20348

[lyahdav]

Per https://github.com/microsoft/react-native-windows/blob/main/packages/playground/windows/playground-win32/Playground-Win32.cpp#L366 this is a Grid. From what you linked there is no GridAutomationPeer. At the point we SetAccessibleRoot we only have that control available. So what makes sense, to set LandmarkTypeProperty or to create some other dummy control? LandmarkTypeProperty seems cleaner.

[chiaramooney]

👍