Fixes T13495. See that task for details.
Tokenizer tokens which contain Chinese glyphs are slightly taller than normal tokens in Firefox 73, and at some non-100% zoom levels in other browsers.
This cauess the tokenizer list to layout and line break oddly.
Fix this by clamping tokenizer sizes more aggressively. Specifying a max-height means they can no longer line wrap, so this also requires more specification of overflow behavior.