Bug 1100238 - [Stingray][smart-system] Allow certified applications take screenshot

Notice: Please igonre the first 2 commits (they're waiting for green try-server to check-in but I included them here for dependency) and just review the third one.

And seems that comments from Tzu-lin (reviewing bug 1098274) can also be seen here but it's not related :-/ After try-server goes green, I will merge 1098162 and 1098274 separately.