[arch-general] google-chrome/chromium and youtube "app"?

Hi all Every so often, when a notification pops up from youtube and I click on it in the plasma's notification area, a separate youtube player window opens. This separate window looks like a chrome app. However, I cannot find this app in my list of chrome apps. No youtube extension or youtube app or similarly named stuff to be found. I find it difficult to get information about in search because of the generic keywords. Anybody know any thing of this and how to disable it? Many thanks Andy "Aethalides" Pieters