Have screen reader acknowledge availability of search results

[atsansone]

Hotlist: https://buganizer.corp.google.com/hotlists/5891206
Bug: https://buganizer.corp.google.com/issues/338010890

Observed Results

The screen reader does not notify anything when the search results are available.

• Screencast.

Expected Results

The screen reader should notify when search results appear, for example "showing 10 search results".

User Impact

Users will not know when results appear which may lead to confusion or lose context if the screen reader does not announce the search results when available. This will affect blind and low vision users who depend on screenreaders.

Steps To Reproduce

1. Enable ChromeVox using Ctrl + Alt + z.
2. Go to https://dart.dev/guides.
3. Using the tab key navigate to "search" field.
4. Search for "isolate" and observe screen reader announcement when the search results appear.

Relevent GAR Sheet

A11Y Tracker.

GAR Details

1.16C Final run through, with Screen reader.

Environment Details

• Machine: Chromebook.
• Browser: Chrome (123.0.6312.112 (Official Build) (64-bit)).
• Accessibility Tool: ChromeVox.
• Bug Filling Time: 10 mins.