Bug 1043275 - Add a meta instruction to the vertical homescreen.

We're adding it back in: https://github.com/etiennesegonzac/gaia/blob/f622c144ac746fcbf08e9fe65d750bca6ba6a56c/apps/system/style/app_titlebar.css#L11

Do you think it's okay to land it as is (as long as we land the titlebar and turn on the settings at the same time)