Initially, it seemed to be a temporary regression. Later that it may be related to Meltdown/Spectre mitigations. Currently, it is well-known to developers and remains patiently waiting for improvement.
https://bugs.chromium.org/p/chromium/issues/detail?id=827497...
> This is a non-regression issue as it is observed from M60 old builds.
No mention of the regression described here. If this is an issue you care about, I suggest you check out the bisect-builds-py tool I linked to.