[CSSOM] Can window.getComputedStyle be extended to match ::placeholder?

[marcysutton]

Hello, I'm wondering if window.getComputedStyle could be extended to match the :placeholder pseudo element. The spec explicitly mentions :before and :after: https://www.w3.org/TR/cssom-1/#extensions-to-the-window-interface

The result of testing live code shows that only Firefox matches :placeholder. An issue in the Chromium bug tracker indicates they consider this to be a bug in Firefox, so I thought I'd pose the question here.

It would be helpful to clarify this for browsers so that accessibility testing tools can audit the color contrast of placeholder text (included by WCAG success criteria 1.4.3).

Update: It looks like :first-letter does get returned by getComputedStyle in most major browsers, so further specification around pseudo-elements would be good. https://codepen.io/AmeliaBR/pen/VyvPoN?editors=1111

[Loirooriol]

I think getComputedStyle should match all supported pseudo-elements.

[FremyCompany]

Merging with #2149