Replace mozilla.widget.use-argb-visuals pref by -moz-gtk-csd-transparent-background media query at browser.css
to draw transparent background. The media query is set by toolkit code and enabled when compatible
window manager is detected.
Differential Revision: https://phabricator.services.mozilla.com/D6658
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extra : moz-landing-system : lando
Values taken from running Firefox on Ubuntu with GTK.
MozReview-Commit-ID: K3aDicUBr8q
--HG--
extra : rebase_source : 3d9634a5398b768d091414ba76e2b8a027689832
Fixes problem with the initial computed value of font-family
being empty and not matching the later value in
test_value_storage.html.
MozReview-Commit-ID: HOHvMZPP1GD
All our widgets support it with a constant true.
MozReview-Commit-ID: JMEItUsxYWq
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extra : rebase_source : e7e0a3f83001813239338bc5b3895252e1fb3ea6
All our widgets support it with a constant true.
MozReview-Commit-ID: JMEItUsxYWq
--HG--
extra : rebase_source : a2661dce1ac191fdf098e631cd7878f0215643d5