We just needed this feature in the browser. When you listen to music online with different services, at times it can be difficult to find the needed tab and then the pause button there. It also very cool when you open another video and music stops automatically for you to watch the video.
We understand that there are tons of other streaming services, that's why we are eager to share the stuff with everybody to enable everybody with this feature.
To compile your dev version, see Chrome Dev Getting Started. There are also lots of useful info there.