Content rendered in regions is not selectable. If you open any of the LayoutTests/fast/regions/ files (such as flow-content-basic.html) and try to select the regions text (which would be the first instance of "flow content" in that file) nothing happens. Trying to select around and/or through the flow content results in bad selection artifacts. Doing a select all does select flow content, but not in display order.
Regions content should be selectable in place, and doing a select all and copy should give you the text in display order.
Hmm. Given that absolute and relative positioned content does not "give you the text in display order" let's drop that part of the expectation from this bug. The only expectation for this bug should be that clicking in the displayed region area should select region content.
This sounds like the repaint area is not calculated correctly. We should also redirect repaints to the correct RenderRegions.
I am currently working on it.
I think this is related to https://bugs.webkit.org/show_bug.cgi?id=66254 .
Fixed with the changes from 66254