Our diff viewer styling used a combination pre-wrap, word-break, and

overflow-wrap to force wrapping of content in diffs. This does a

pretty good job, but if there's a line with a very large number of

spaces, browsers will keep those spaces grouped together and force the

width of the diff viewer to be too wide.
This updates our code to now optimistically use break-spaces, which is

like pre-wrap but will also break spaces. While this isn't supported

on all browsers, it is supported on most, and we fall back to the

existing pre-wrap behavior anyway.
It also fixes the value for overflow-wrap to use the correct mode (the

original mode used wasn't actually valid for this property, and caused

us to fall back on word-break's behavior exclusively).

Tested with some sample diffs from a customer who hit this issue. Verified

that this fixed the line wrapping and table width issues we've heard about.
Tested on Chrome, Firefox, and Safari.