a11y module describes series on each redraw, even if nothing changed

[pawellysy]

Expected behaviour

The a11y function should fire only, when something changed in the chart.

Actual behaviour

A11y's SeriesDescriber.DescribeSeries method is fired on each redraw, even though nothing changed.

Live demo with steps to reproduce

https://jsfiddle.net/BlackLabel/kw5bpa9x/1/

Visit this demo, open console, and leave logpoint in the SeriesDescriber.describeSeries.
Click anywhere in the chart's plotArea

see, that after every redraw, which is fired on click, the method above is fired.

Product version

Affected browser(s)

v11.2

[oysteinmoseng]

Internal note: It should only be necessary to re-describe if the rendering of the series has changed (e.g. which points are visible, or their location). For example after changing the data, the visibility of series, or zooming.

Is this a performance issue at the moment, or is it related to a workaround making use of the describeSeries function?