Bug 1023312 - [Vertical homescreen] Smart collection viewing fails on th...

...e flame because e.me server fails to return background. [r=amirn]

http://bugzil.la/1023312
> I disagree that device.screen should be updated as flooring serves the bgimage request only. It's not a general setting.

we will also be sending it in the `ctx` https://github.com/mozilla-b2g/gaia/pull/20360/files#diff-d74a96f34da61587fd1fb742964e2dc0R30
but I agree we should not round if it doesn't cause errors