Bug 1720621 - Adjust display list building rect for page scale transform within nsPageContentFrame. r=miko

Differential Revision: https://phabricator.services.mozilla.com/D120127

layout/generic/nsPageContentFrame.cpp

@@ -350,6 +350,11 @@ void nsPageContentFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
       BuildPreviousPageOverflow(aBuilder, pageFrame, this, set);
     }
 
+    nsRect visible = aBuilder->GetVisibleRect();
+    visible.ScaleInverseRoundOut(PresContext()->GetPageScale());
+
+    nsDisplayListBuilder::AutoBuildingDisplayList buildingForChild(
+       aBuilder, this, visible, visible);
     mozilla::ViewportFrame::BuildDisplayList(aBuilder, set);
 
     set.SerializeWithCorrectZOrder(&content, GetContent());