A new developer effort to help differentiate between web and other apps on ChromeOS is in the works. The feature request was added to Google’s queue on March 30 but coding hasn’t started yet. However, today the request was assigned to a developer. The change as it’s now proposed will use squircles for ChromeOS web app icons. I don’t think that’s the way to go.

Source: Finally: ChromeOS web app icons will look different on Chromebooks