The implementation of isValidMarkerStyleProperty() in PropertyCascade.cpp only supports a small list of properties from an old Editor's draft (25 July 2017). The latest draft (https://drafts.csswg.org/css-lists-3/#marker-properties as of this writing) now says this:

    3.1.1. Properties Applying to ::marker

    All properties can be set on a ::marker pseudo-element and will have a computed value; however, only the following CSS properties actually apply to a marker box:

    - the text-combine-upright, unicode-bidi, and direction properties
    - the content property
    - all animation and transition properties

We should update our implementation to match this.