Internal bug: b/145715671

Repro:

• Turn on Talkback.
• Create a barrier dismissable dialog via Flutter on iOS 13.2.

Note that:

• The initial focus is on entire screen (or in some cases on the system clock).
• Unable to move the focus to the dialog by using swipes.
• Tapping into the dialog moves the focus as expected.

Expected Behavior:

• Should be able to swipe and highlight the dialog elements.
• If the dialog is not dismissable, a11y correctly focuses on the elements in the dialog first. We would expect the same behavior from a dismissable dialog. Initial focus should be on the dialog title. Swiping should cycle through the elements including dialog buttons and "screen" (dismiss action).