Changing a collapsed border's width should change the width of the table and the width of a shrink-to-fit containing block.
There should be a square with a 4px inner blue border and a 1px outer black border.
Firefox 50.0a1 (nightly 2016-07-14) fails this, so it should probably be upstreamed, except it uses chrome-specific `runAfterLayoutAndPaint`.
PASS