Bug 1761995 - Skip content-visibility: hidden content in display lists r=emilio

Differential Revision: https://phabricator.services.mozilla.com/D142341

layout/generic/nsSubDocumentFrame.cpp

@@ -351,6 +351,10 @@ void nsSubDocumentFrame::BuildDisplayList(nsDisplayListBuilder* aBuilder,
     return;
   }
 
+  if (IsContentHidden()) {
+    return;
+  }
+
   // If we're passing pointer events to children then we have to descend into
   // subdocuments no matter what, to determine which parts are transparent for
   // hit-testing or event regions.