--- a/layout/base/nsCSSFrameConstructor.cpp
+++ b/layout/base/nsCSSFrameConstructor.cpp
@@ -5559,32 +5559,16 @@ nsCSSFrameConstructor::AddFrameConstruct
     return;
   }
   RefPtr<ComputedStyle> computedStyle = ResolveComputedStyle(aContent);
   DoAddFrameConstructionItems(aState, aContent, computedStyle,
                               aSuppressWhiteSpaceOptimizations, parentFrame,
                               nullptr, aItems);
 }
 
-void
-nsCSSFrameConstructor::SetAsUndisplayedContent(nsFrameConstructorState& aState,
-                                               FrameConstructionItemList& aList,
-                                               nsIContent* aContent,
-                                               ComputedStyle* aComputedStyle,
-                                               bool aIsGeneratedContent)
-{
-  if (aComputedStyle->GetPseudo()) {
-    if (aIsGeneratedContent) {
-      aContent->UnbindFromTree();
-    }
-    return;
-  }
-  MOZ_ASSERT(!aIsGeneratedContent, "Should have had pseudo type");
-}
-
 // Whether we should suppress frames for a child under a <select> frame.
 //
 // Never create frames for non-option/optgroup kids of <select> and non-option
 // kids of <optgroup> inside a <select>.
 // XXXbz it's not clear how this should best work with XBL.
 static bool
 ShouldSuppressFrameInSelect(const nsIContent* aParent,
                             const nsIContent* aChild)
@@ -5712,22 +5696,32 @@ nsCSSFrameConstructor::AddFrameConstruct
         if (overridenNamespace == kNameSpaceID_XUL) {
           tag = overridenTag;
         }
       }
     }
   }
 
   const bool isGeneratedContent = !!(aFlags & ITEM_IS_GENERATED_CONTENT);
+  MOZ_ASSERT(!isGeneratedContent || computedStyle->GetPseudo(),
+             "Generated content should be a pseudo-element");
+
+  FrameConstructionItem* item = nullptr;
+  auto cleanupGeneratedContent = mozilla::MakeScopeExit([&]() {
+    if (isGeneratedContent && !item) {
+      MOZ_ASSERT(!IsDisplayContents(aContent),
+                 "This would need to change if we support display: contents "
+                 "in generated content");
+      aContent->UnbindFromTree();
+    }
+  });
 
   // Pre-check for display "none" - if we find that, don't create
   // any frame at all
   if (display->mDisplay == StyleDisplay::None) {
-    SetAsUndisplayedContent(aState, aItems, aContent, computedStyle,
-                            isGeneratedContent);
     return;
   }
 
   if (display->mDisplay == StyleDisplay::Contents) {
     if (aParentFrame) {
       // FIXME(emilio): Pretty sure aParentFrame can't be null here.
       aParentFrame->AddStateBits(NS_FRAME_MAY_HAVE_GENERATED_CONTENT);
     }
@@ -5753,32 +5747,26 @@ nsCSSFrameConstructor::AddFrameConstruct
                                aItems);
     return;
   }
 
   bool isText = !aContent->IsElement();
 
   nsIContent* parent = aParentFrame ? aParentFrame->GetContent() : nullptr;
   if (ShouldSuppressFrameInSelect(parent, aContent)) {
-    if (!isText) {
-      SetAsUndisplayedContent(aState, aItems, aContent, computedStyle,
-                              isGeneratedContent);
-    }
     return;
   }
 
   // When constructing a child of a non-open <details>, create only the frame
   // for the main <summary> element, and skip other elements.  This only applies
   // to things that are not roots of native anonymous subtrees (except for
   // ::before and ::after); we always want to create "internal" anonymous
   // content.
   auto* details = HTMLDetailsElement::FromNodeOrNull(parent);
   if (ShouldSuppressFrameInNonOpenDetails(details, aContent)) {
-    SetAsUndisplayedContent(aState, aItems, aContent, computedStyle,
-                            isGeneratedContent);
     return;
   }
 
   bool isPopup = false;
   // Try to find frame construction data for this content
   const FrameConstructionData* data;
   if (isText) {
     data = FindTextData(aParentFrame);
@@ -5790,18 +5778,16 @@ nsCSSFrameConstructor::AddFrameConstruct
     Element* element = aContent->AsElement();
 
     // Don't create frames for non-SVG element children of SVG elements.
     if (namespaceId != kNameSpaceID_SVG &&
         ((aParentFrame &&
           IsFrameForSVG(aParentFrame) &&
           !aParentFrame->IsFrameOfType(nsIFrame::eSVGForeignObject)) ||
          (aFlags & ITEM_IS_WITHIN_SVG_TEXT))) {
-      SetAsUndisplayedContent(aState, aItems, element, computedStyle,
-                              isGeneratedContent);
       return;
     }
 
     data = FindHTMLData(element, tag, namespaceId, aParentFrame,
                         computedStyle);
     if (!data) {
       data = FindXULTagData(element, tag, namespaceId, computedStyle);
     }
@@ -5823,57 +5809,52 @@ nsCSSFrameConstructor::AddFrameConstruct
     // And general display types
     if (!data) {
       data = FindDisplayData(display, element, computedStyle);
     }
 
     MOZ_ASSERT(data, "Should have frame construction data now");
 
     if (data->mBits & FCDATA_SUPPRESS_FRAME) {
-      SetAsUndisplayedContent(aState, aItems, element, computedStyle, isGeneratedContent);
       return;
     }
 
 #ifdef MOZ_XUL
     if ((data->mBits & FCDATA_IS_POPUP) &&
         (!aParentFrame || // Parent is inline
          !aParentFrame->IsMenuFrame())) {
       if (!aState.mPopupItems.containingBlock &&
           !aState.mHavePendingPopupgroup) {
-        SetAsUndisplayedContent(aState, aItems, element, computedStyle,
-                                isGeneratedContent);
         return;
       }
 
       isPopup = true;
     }
 #endif /* MOZ_XUL */
   }
 
   uint32_t bits = data->mBits;
 
   // Inside colgroups, suppress everything except columns.
   if (aParentFrame && aParentFrame->IsTableColGroupFrame() &&
       (!(bits & FCDATA_IS_TABLE_PART) ||
        display->mDisplay != StyleDisplay::TableColumn)) {
-    SetAsUndisplayedContent(aState, aItems, aContent, computedStyle, isGeneratedContent);
     return;
   }
 
   bool canHavePageBreak =
     (aFlags & ITEM_ALLOW_PAGE_BREAK) && aState.mPresContext->IsPaginated() &&
     !display->IsAbsolutelyPositionedStyle() &&
     !(aParentFrame && aParentFrame->IsGridContainerFrame()) &&
     !(bits & FCDATA_IS_TABLE_PART) && !(bits & FCDATA_IS_SVG_TEXT);
 
   if (canHavePageBreak && display->mBreakBefore) {
     AddPageBreakItem(aContent, aItems);
   }
 
-  FrameConstructionItem* item = nullptr;
   if (details && details->Open()) {
     auto* summary = HTMLSummaryElement::FromNode(aContent);
     if (summary && summary->IsMainSummary()) {
       // If details is open, the main summary needs to be rendered as if it is
       // the first child, so add the item to the front of the item list.
       item = aItems.PrependItem(this, data, aContent, pendingBinding,
                                 computedStyle.forget(),
                                 aSuppressWhiteSpaceOptimizations,

--- a/layout/base/nsCSSFrameConstructor.h
+++ b/layout/base/nsCSSFrameConstructor.h
@@ -2113,27 +2113,16 @@ private:
   // may be constructed based on tag, not based on aDisplay!
   bool IsValidSibling(nsIFrame*              aSibling,
                       nsIContent*            aContent,
                       mozilla::StyleDisplay& aDisplay);
 
   void QuotesDirty();
   void CountersDirty();
 
-  /**
-   * Add the pair (aContent, aComputedStyle) to the undisplayed items
-   * in aList as needed.  This method enforces the invariant that all
-   * styles in the undisplayed content map must be non-pseudo contexts and also
-   * handles unbinding undisplayed generated content as needed.
-   */
-  void SetAsUndisplayedContent(nsFrameConstructorState& aState,
-                               FrameConstructionItemList& aList,
-                               nsIContent* aContent,
-                               ComputedStyle* aComputedStyle,
-                               bool aIsGeneratedContent);
   // Create touch caret frame.
   void ConstructAnonymousContentForCanvas(nsFrameConstructorState& aState,
                                           nsIFrame* aFrame,
                                           nsIContent* aDocElement);
 
 public:
 
   friend class nsFrameConstructorState;