Today, the display list interface itself uses Skia interfaces. Some of the interfaces work on Skia types by reference instead of by value. Furthermore, some of the reference types cannot be introspected.

Graphics packages that are not Skia have to re-interpret the Skia type where possible. This actually works in a vast majority of situations. But, in the few cases where this is not possible (filters for instance), the display list interface has to be worked around using side channels.

To be graphics neutral, the display list interface itself must be Skia agnostic. Additionally, it is desirable to use value semantics.

This issue is an elaboration of one if the work items in #85737. Using value semantics will also enable making more of the action items in the section on efficiency in the issue easier to accomplish.