wbr should cut through nowrap unconditionally

[fantasai]

HTML spec specifies

nobr wbr { white-space: normal; }

However, Blink, Presto, WebKit, and IE6 all break through both nobr elements and other elements with white-space: nowrap.

See testcase http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=8755

Just removing the nobr from that selector should be sufficient to fix this.

[domenic]

Although that's probably a good quick-fix to help align with observable behavior, the real issue here is #221, which I tried to fix in #2298 but got stuck on. (And that PR doesn't include this subtlety.)

See http://software.hixie.ch/utilities/js/live-dom-viewer/?saved=8756 .