I don't know what API(s) are being used by the browser to disable video playback, but there are only a few probable options:
(a) The API is different between telling Unity7 and Gnome Shell to not blank, and Chrome doesn't support the latter; or
(b) The API is different between telling Unity7 and Gnome Shell to not blank, and Chrome does support both but gnome-shell is ignoring it; or
(c) The API is the same for both Unity7 and Gnome Shell, and gnome-shell is ignoring it.
So yeah, in both (b) and (c) we would need a gnome-shell task. But there are many possible reasons as to why this is broken. Needs more research.
Sorry, that's the opposite of your problem :)
Back on topic with this bug...
I don't know what API(s) are being used by the browser to disable video playback, but there are only a few probable options:
(a) The API is different between telling Unity7 and Gnome Shell to not blank, and Chrome doesn't support the latter; or
(b) The API is different between telling Unity7 and Gnome Shell to not blank, and Chrome does support both but gnome-shell is ignoring it; or
(c) The API is the same for both Unity7 and Gnome Shell, and gnome-shell is ignoring it.
So yeah, in both (b) and (c) we would need a gnome-shell task. But there are many possible reasons as to why this is broken. Needs more research.