8262981: Create implementation for NSAccessibilitySlider protocol

[Autumn808]

Clean backport JDK-8256108 part of 28.

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Progress

• Change must be properly reviewed (1 review required, with at least 1 Reviewer)
• Change must not contain extraneous whitespace
• Commit message must refer to an issue

Issue

• JDK-8262981: Create implementation for NSAccessibilitySlider protocol

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk11u-dev pull/1570/head:pull/1570
$ git checkout pull/1570

Update a local copy of the PR:
$ git checkout pull/1570
$ git pull https://git.openjdk.org/jdk11u-dev pull/1570/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 1570

View PR using the GUI difftool:
$ git pr show -t 1570

Using diff file

Download this PR as a diff file:
https://git.openjdk.org/jdk11u-dev/pull/1570.diff

[bridgekeeper]

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[openjdk]

This backport pull request has now been updated with issue from the original commit.