Add onSlidingComplete callbacks when sliders adjusted via a11y

[marcmulcahy]

Summary

When sliders are adjusted via accessibility, no onSlidingComplete callback is
generated. This causes problems for components which perform behavior in this
callback, and means that such components don't behave properly when adjusted via
accessibility. For example, if an app hosting a volume control slider only commits the volume change to the hardware on onSlidingComplete, it is impossible for a screen reader user to ever actually adjust the volume.

Ensure that sliders call the onSlidingComplete callback after adjusted via
accessibility.

Changelog

[General] [Fix] - Add onSlidingComplete callbacks when sliders adjusted via a11y.

[CATEGORY] [TYPE] - Message

Test Plan

Prior to this change, using the RNTester slider example with a screen reader, the onSlidingComplete callback tests never shows any callbacks when the slider is adjusted. With this change applied, the callback test will show a number of callbacks corresponding to the number of times the slider was adjusted via the screen reader.

[pull-bot]

Messages

📖

📋 Verify Changelog Format - A changelog entry has the following format: [CATEGORY] [TYPE] - Message. CATEGORY may be: General iOS Android JavaScript Internal (for changes that do not need to be called out in the release notes) TYPE may be: Added, for new features. Changed, for changes in existing functionality. Deprecated, for soon-to-be removed features. Removed, for now removed features. Fixed, for any bug fixes. Security, in case of vulnerabilities. MESSAGE may answer "what and why" on a feature level. Use this to briefly tell React Native users about notable changes.

Generated by 🚫 dangerJS against 8c84437

[cpojer]

Thank you!

[facebook-github-bot]

@cpojer is landing this pull request. If you are a Facebook employee, you can view this diff on Phabricator.

[react-native-bot]

This pull request was successfully merged by Marc Mulcahy in c7aa6dc.

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