The feature enables you to serve local pages to a mobile device
One of the things the Google Chrome team has been working on lately is better dev tools. While the dev tools in Chrome still remain the gold standard, Google thought it could do better and integrate the tools more naturally into the workflow of the regular web developer.One of the big ways it's achieving this is via the new workspaces feature. The idea is to make it possible to work with local files and have any change you make forwarded and visible in the browser instantly.
At the same time, the team is also working on making mobile development easier by, for example, being able to push a local file to a mobile device without setting up an open web server.
This is done via port forwarding, which is relatively easy to set up. Incidentally, in the latest Chromium builds, a default port for port forwarding has been chosen, the generic 8080.