Slider `aria-valuetext` does not update when `constrainValue` option is used.

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When the constrainValue option is used for a Slider, aria-valuetext does not update in A11y View. I'm wondering if this regression was introduced when #698 was addressed.

For example in calculus-grapher,CurveManipulationWidthSlider does not update in A11y View. If I comment of the usage of constrainValue, it does update in A11y View. CurveManipulationWidthSlider looks like this in Calculus Grapher:

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Hmm... I tried some other sliders that use constrainValue, and I don't see this problem. So I guess it's likely that this is somehow specific to CurveManipulationWidthSlider. If so, I can't identify what's wrong.