[css-contain-3] "container width" and "container height" units #5888
Description
Viewport-relative units (such as vh and vw) are commonly used among UI design for sizing and spacing of elements.
With the new container queries spec, authors will want to use such units as container-height (ch) and container-width (cw) for container-based sizing.
An example is using cw units in srcset similarly to how one would use vw units in srcset. Percentages would not work in that instance, as the value needs to be absolute or relative length.
Edit: ch would not work as a unit name due to the existing ch (character) unit