These were imported in bug 170713 and marked as failing. Current patches for bug 182230 and bug 182053 do not help. I'm opening this for the record.
For the record, these WPT tests were added by Chromium developers in https://bugs.chromium.org/p/chromium/issues/detail?id=665927
The problem is that OverflowClip on the body depends on the one on the html element (see RenderBox::updateFromStyle()) so it makes handling dynamic update a bit more complicated. See especially https://bugs.chromium.org/p/chromium/issues/detail?id=665927#c23
In the patch for bug 182053, I'm using computedStyle() to determine the scrollingElement, which allows to always return the correct value. However, the CSS used values for overflow may still be incorrect after dynamic change which is why these tests are failing.