Bug 1942715: Part 4 - Switch to using a more transparent wrapper. r=firefox-style-system-reviewers,emilio

Don't have to write more one-off wrappers for size and margin.
It does cost having to copy fallback values, but that may
not be a huge tradeoff.

Differential Revision: https://phabricator.services.mozilla.com/D237097

layout/base/PresShell.cpp

@@ -3833,7 +3833,7 @@ bool PresShell::ScrollFrameIntoView(
     const auto positionProperty = aFrame->StyleDisplay()->mPosition;
     for (auto side : AllPhysicalSides()) {
       if (stylePosition->GetAnchorResolvedInset(side, positionProperty)
-              .IsAuto()) {
+              ->IsAuto()) {
         continue;
       }
       // See if this axis is stuck.