The attached test has one named flow with a two-column layout applied to it. The content is monolithic that flows through two regions and overflows the last region. Result: The content flows through the first column in the first region, does not wrap into its second column, then flows into the first column of the second region, and overflows the bottom of that column Expected: It should flow through each of the two columns of the first region, then through each of two columns, and overflow into a fourth column. If the regions are removed and the content is a child of the multicol container, this is the behavior.
Created attachment 210531 [details] test file for bug
Created attachment 210532 [details] reference file for test
Multicolumn inside regions.
CSS Regions were removed in Bug 174978.