R1:1da54837ea8a

Improve line breaking behavior in Firefox and Chrome under complex conditions

Summary: See <https://github.com/phacility/phabricator/pull/854>. In some situations, `line-break: anywhere` produces better behavior than `word-break: break-all`. It never appears to produce worse behavior.

Test Plan:
- Break behavior changes if a line contains "<span />" elements caused by syntax highlighting. This CSS adjustment only appears to apply to text with internal "<span />" elements.
- This specifically impacts…