[css-overflow-4] Make sure the interaction between the continue property and OM is well defined. #2970
Description
Maybe the fact that the spec says “The remaining content after the fragmentation break is discarded, similar to if it were display: none” is sufficient to infer everything that happens to the OM and various APIs. But leaving it at maybe isn't great, so we should make sure. Being explicit about the effects is a good thing regardless.