This is Material Design for Chrome, first rolling out to Chrome OS

Update 4/25: Chrome 50 for Android is rolling out now with the ability to pause and cancel downloads from the notification shade.
Chrome 50 is rolling out now to Mac, Windows, and Linux. The latest version of the browser contains the usual bug and security fixes, but also features an update to improve the reliability of push notifications and speed up page load.
With Chrome 49 fully rolled out to desktops, Android, and Chrome OS, version 50 is now in the beta channel. It is expected to bring Material Design to the browser and introduce improved push notifications and other developer focused features.