The Google Hangouts extension has a panel that shows up outside of the Chrome UI.
It is sort of like a notification but not. I don't see anything in the Extension Developer Docs that describes an API to make this work. Is this a Google-specific hack they're doing? Is there something in the experimental APIs that I'm missing?
It is an options of chrome.windows.create. Make sure you set
type
topanel
.panel
may not be supported on all platforms and you may have to specifically enable panels in Chrome Flagschrome://flags/#enable-panels
.