Screenshots are disabled by default in Google Chrome’s incognito mode on Android, which, while good for privacy, can be inconvenient now and then. You can use a workaround via Chrome flags to take incognito screenshots, but this trick creates a new problem—doing so exposes those incognito tabs in the “Recents” screen…
Source: LifeHacker – The New, Better Way to Take Screenshots in Chrome’s Incognito Mode on Android