Earlier this week Google released Chrome 71, however, the latest release still lacks support for Dark Mode on macOS Mojave, fortunately, it appears that this update will come in early 2019.
As mentioned on Reddit, a Google developer recently submitted a code change that implements system-level Dark Mode in Chromium; the open source web browser that serves as the foundation of Google Chrome. The code change passed the review process and will make its way into the future release of Chrome.
For those who are unaware, there are several different builds of Chrome that Google uses to slowly test and roll out new features. All code changes begin in Chromium and then work their way from Canary to Chrome Dev to Chrome Beta and then to Chrome, where the stable version release to all users roughly every six weeks.
The system-level Dark Mode applies a dark appearance to much of the Chrome interface including the Omnibox, tabs, menu, bookmark bar, status bar, and dialogue boxes. The startup page with Google search and shortcuts will also have a black background when the Dark theme is enabled in System Preferences. Most of the current Dark Mode colours in Chromium are placeholders, according to one developer that's working on the project, so there may be slight changes to come.
One challenge that the developers face is ensuring that the Dark Mode is distinguishable from Chrome's private-browsing Incognito Mode, which is also dark. We are not entirely sure when this iteration of the Chrome update will be available, but it might come with the Chrome 73 update. In the meantime, a variety of third-party dark themes are available for Chrome, but the Omnibox always remains white since it is not allowed to be themed.