Bug 1623792 - Pt 7 - Remove space snapper from stacking context stack. r=aosmond
Bug 1623792 - Pt 7 - Remove space snapper from stacking context stack. r=aosmond

There doesn't seem to be any need to have this per stacking context, as
the device pixel ratio is always the same during scene building (the
previous code just clones this object as each stacking context is
pushed).

Differential Revision: https://phabricator.services.mozilla.com/D84113

[ghsync] From https://hg.mozilla.org/mozilla-central/rev/9d195ff03a52e46975128b3c3a998aed0c090a85

servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender,servo/webrender