Gregory's Server@sophieschmieg precisely. Also: it's a graph theory peg being rammed into a source control hole.
Chrome at least gives us a bunch of common functionality that sands *some* of the sharp edges off of it, but it's still awful to use and I'm still learning tricks that make my experience with it less painful five years after starting with it.
@tess the fact that Chrome/gerrit and GitHub actually take different parts of git to mean certain things (in Gerrit you have individual commits as the thing that gets reviewed, with branches being used for separate versions, in GitHub it's branches and pull requests that get reviewed instead) is also a great sign that this isn't the best source control could be.
And really, code review should be a first class citizen for a source control system anyways, and not tacked on by third party tooling