I can't actually see it, but I believe this ticket[0] in the Chromium bugtracker is for Spectre mitigations (in V8). If you search in the V8 commit log for BUG=chromium:798964, you'll find a number of commits affecting most of the backends (and if you're really looking, you'll also see related or similar commits which are no longer tagged with the bug number, later in the log)

[0]: https://bugs.chromium.org/p/chromium/issues/detail?id=798964