Bikeshed update for 'Specify the behaviour when the scrollSource does not have a CSS layout box. Fixes issue #3.' [ci skip]

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commit ba92cbb
Author: Botond Ballo <botond@mozilla.com>
Date:   Wed Mar 22 14:59:07 2017 -0400

    Specify the behaviour when the scrollSource does not have a CSS layout box. Fixes issue #3.

Author: theres-waldo