Bug

Demo URL (required)*:
Angular Material demos for mat autocomplete.
https://material.angular.io/components/autocomplete/examples

Detailed Reproduction Steps

1. Enable VoiceOver screen reader.
2. Open the angular demo for mat-autocomplete in angular material in chrome. https://material.angular.io/components/autocomplete/examples
3. Pick one of the examples and trigger the autocomplete option drop-list.
4. Use the keyboard to move between different options and listen to screen reader.

Explain the expected behavior

The VoiceOver screen reader should announce the index of each option.

Explain the current behavior

The VoiceOver screen reader only announces the option label + "clickable" without index.

Discuss the use-case or motivation for changing the existing behavior

This feature to impacts user accessibility experience.

List the affected versions of AngularJS, Material, OS, and browsers

• AngularJS: 10.0.0
• AngularJS Material: 10.0.0
• OS: macOS Catalina Version 10.15.3
• Browsers: Chrome Version 83.0.4103.116 (Official Build) (64-bit)

Add anything else we should know

Adding roles described in
https://www.w3.org/TR/wai-aria-practices/examples/combobox/aria1.0pattern/combobox-autocomplete-both.html does not fix the issue.