[Android] Talkback screenreader does not obey `FocusTrap`

[lin-brian-l]

Is this a regression?

• Yes, this behavior used to work in the previous version

The previous version in which this bug was not present was

No response

Description

ConfigurableFocusTrap.focusInitialElementWhenReady() successfully traps the user's focus on an element on Chrome, but it does not trap the focus of the Talkback screenreader. See the attached videos for details.

Demos

Chrome - focus is trapped within the modal

Screencast.2023-10-03.16.11.22.mp4

Talkback - focus is not trapped within the modal

XRecorder_03102023_160944.mp4

Reproduction

StackBlitz link
Steps to reproduce:

1. Activate Talkback
2. In the demo app, click on the "Open Modal" button
3. Tab through the elements in the modal by swiping right.

Expected Behavior

Focus behavior should match Desktop, where it cannot leave the modal.

Actual Behavior

On Talkback, focus behavior leaves the modal and phone elements can be focused.

Environment

• Angular: 16.2.7
• CDK/Material: 16.2.6
• Browser(s): Chrome
• Operating System (e.g. Windows, macOS, Ubuntu): Android