Now the spec cleary says that we don't need to propagate body's
scroll-padding value to the document viewport since
https://github.com/w3c/csswg-drafts/issues/3740, so we don't need to care about
GetViewportScrollStylesOverrideElement() at all.
This change fixes the crash test case in this commit, but it's not sufficient.
In the next patch, we will fix another crash case.
Differential Revision: https://phabricator.services.mozilla.com/D27422
--HG--
extra : moz-landing-system : lando
Hiroyuki Ikezoe