--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -3627,22 +3627,17 @@ nsDisplaySubDocument::BuildLayer(nsDispl
     nsRect displayport, criticalDisplayport;
     ViewID scrollId = FrameMetrics::NULL_SCROLL_ID;
     if (rootScrollFrame) {
       nsIContent* content = rootScrollFrame->GetContent();
       if (content) {
         usingDisplayport = nsLayoutUtils::GetDisplayPort(content, &displayport);
         usingCriticalDisplayport =
           nsLayoutUtils::GetCriticalDisplayPort(content, &criticalDisplayport);
-
-        if (isRootContentDocument) {
-          scrollId = nsLayoutUtils::FindOrCreateIDFor(content);
-        } else {
-          nsLayoutUtils::FindIDFor(content, &scrollId);
-        }
+        scrollId = nsLayoutUtils::FindOrCreateIDFor(content);
       }
     }
 
     nsRect viewport = mFrame->GetRect() -
                       mFrame->GetPosition() +
                       mFrame->GetOffsetToCrossDoc(ReferenceFrame());
 
     container->SetScrollHandoffParentId(mScrollParentId);