The elementtiming attribute is used to indicate that an element is flagged for tracking by PerformanceObserver objects using the "element" type. For more details, see the PerformanceElementTiming interface.
This attribute may be applied to <img>, <image> elements inside an <svg>, poster images of <video> elements, elements which have a background-image, and elements containing text nodes, such as a <p>.
In the DOM, this attribute is reflected as Element.elementTiming.