Just came across this & don't remember seeing it mentioned on here. This is an “opt-in” feature that claims that it might be able to speed up your YouTube buffering. It’s an official YouTube program so there’s some real promise in it.
A quote from the link below: "This is an opt-in beta for "Feather" support on YouTube. The "Feather" project is intended to serve YouTube video watch pages with the lowest latency possible. It achieves this by severely limiting the features available to the viewer and making use of advanced web techniques for reducing the total amount of bytes downloaded by the browser. It is a work in progress and may not work for all videos."
Tapped from a Nexus