diff --git a/layout/base/nsLayoutUtils.cpp b/layout/base/nsLayoutUtils.cpp
index c1f34d4aa4ed..a86855f29a99 100644
--- a/layout/base/nsLayoutUtils.cpp
+++ b/layout/base/nsLayoutUtils.cpp
@@ -1227,49 +1227,6 @@ nsLayoutUtils::GetDisplayPortForVisibilityTesting(
   return usingDisplayPort;
 }
 
-/* static */ nsRect
-nsLayoutUtils::GetDisplayPortOrFallbackToScrollPort(nsIScrollableFrame* aScrollableFrame)
-{
-  MOZ_ASSERT(aScrollableFrame);
-
-  nsIFrame* scrollableFrameAsFrame = do_QueryFrame(aScrollableFrame);
-  MOZ_ASSERT(scrollableFrameAsFrame);
-
-  nsIContent* contentForDisplayPort = scrollableFrameAsFrame->GetContent();
-  MOZ_ASSERT(contentForDisplayPort);
-
-  nsRect displayPort;
-  bool usingDisplayPort =
-    GetDisplayPortForVisibilityTesting(contentForDisplayPort,
-                                       &displayPort,
-                                       RelativeTo::ScrollFrame);
-
-  return usingDisplayPort ? displayPort
-                          : aScrollableFrame->GetScrollPortRect();
-}
-
-/* static */ nsRect
-nsLayoutUtils::TransformAndIntersectRect(nsIFrame* aFrom,
-                                         const nsRect& aFromRect,
-                                         nsIFrame* aTo,
-                                         const nsRect& aToRect)
-{
-  if (MOZ_UNLIKELY(!aFrom)) {
-    return nsRect();  // Treat as no intersection.
-  }
-  if (MOZ_UNLIKELY(!aTo)) {
-    return nsRect();  // Treat as no intersection.
-  }
-
-  nsRect fromRectInToSpace = aFromRect;
-  TransformResult result = TransformRect(aFrom, aTo, fromRectInToSpace);
-  if (MOZ_UNLIKELY(result != TransformResult::TRANSFORM_SUCCEEDED)) {
-    return nsRect();  // Treat as no intersection.
-  }
-
-  return aToRect.Intersect(fromRectInToSpace);
-}
-
 bool
 nsLayoutUtils::SetDisplayPortMargins(nsIContent* aContent,
                                      nsIPresShell* aPresShell,
@@ -3313,49 +3270,7 @@ nsLayoutUtils::GetAsyncScrollableAncestorFrame(nsIFrame* aTarget)
   uint32_t flags = nsLayoutUtils::SCROLLABLE_ALWAYS_MATCH_ROOT
                  | nsLayoutUtils::SCROLLABLE_ONLY_ASYNC_SCROLLABLE
                  | nsLayoutUtils::SCROLLABLE_FIXEDPOS_FINDS_ROOT;
-  return GetNearestScrollableFrame(aTarget, flags);
-}
-
-nsIScrollableFrame*
-nsLayoutUtils::GetAsyncScrollableProperAncestorFrame(nsIFrame* aTarget)
-{
-  nsIFrame* parent = GetCrossDocParentFrame(aTarget);
-  if (!parent) {
-    return nullptr;
-  }
-
-  return GetAsyncScrollableAncestorFrame(parent);
-}
-
-/* static */ nsIFrame*
-nsLayoutUtils::GetAsyncScrollableProperAncestorFrameOrFallback(nsIFrame* aTarget)
-{
-  MOZ_ASSERT(aTarget);
-
-  nsIScrollableFrame* scrollableFrame =
-    GetAsyncScrollableProperAncestorFrame(aTarget);
-  if (scrollableFrame) {
-    return do_QueryFrame(scrollableFrame);  // We got an actual scrollable frame.
-  }
-
-  if (aTarget->PresContext()->Document()->IsHTMLDocument()) {
-    // Don't fall back for HTML documents, which should have a root scrollable
-    // frame.
-    return nullptr;
-  }
-
-  // We'll have to fall back to the root frame.
-  nsIPresShell* presShell = aTarget->PresContext()->GetPresShell();
-  if (!presShell) {
-    return nullptr;
-  }
-
-  nsIFrame* rootFrame = presShell->GetRootFrame();
-  if (rootFrame == aTarget) {
-    return nullptr;  // Exclude |aTarget| itself.
-  }
-
-  return rootFrame;  // May be null.
+  return nsLayoutUtils::GetNearestScrollableFrame(aTarget, flags);
 }
 
 void
diff --git a/layout/base/nsLayoutUtils.h b/layout/base/nsLayoutUtils.h
index 9be53083c684..3db939d72508 100644
--- a/layout/base/nsLayoutUtils.h
+++ b/layout/base/nsLayoutUtils.h
@@ -210,12 +210,6 @@ public:
     nsRect* aResult,
     RelativeTo aRelativeTo = RelativeTo::ScrollPort);
 
-  /**
-   * @return the critical displayport associated with @aScrollableFrame, or if
-   * it does not have a displayport, the associated scrollport.
-   */
-  static nsRect GetDisplayPortOrFallbackToScrollPort(nsIScrollableFrame* aScrollableFrame);
-
   enum class RepaintMode : uint8_t {
     Repaint,
     DoNotRepaint
@@ -918,16 +912,6 @@ public:
   static TransformResult TransformRect(nsIFrame* aFromFrame, nsIFrame* aToFrame,
                                        nsRect& aRect);
 
-  /**
-   * Transforms @aFromRect from the space of @aFrom to the space of @aTo, and
-   * intersects it with @aToRect.
-   *
-   * @return The result of the intersection, or the empty rect if
-   * TransformRect would've returned something other than TRANSFORM_SUCCEEDED.
-   */
-  static nsRect TransformAndIntersectRect(nsIFrame* aFrom, const nsRect& aFromRect,
-                                          nsIFrame* aTo, const nsRect& aToRect);
-
   /**
    * Get the border-box of aElement's primary frame, transformed it to be
    * relative to aFrame.
@@ -2729,25 +2713,8 @@ public:
   static void MaybeCreateDisplayPort(nsDisplayListBuilder& aBuilder,
                                      nsIFrame* aScrollFrame);
 
-  /**
-   * @return the nearest async scrollable ancestor frame of @aTarget, including
-   * @aTarget itself if @aTarget is async scrollable.
-   */
   static nsIScrollableFrame* GetAsyncScrollableAncestorFrame(nsIFrame* aTarget);
 
-  /**
-   * @return the nearest async scrollable ancestor frame of @aTarget, excluding
-   * @aTarget itself.
-   */
-  static nsIScrollableFrame* GetAsyncScrollableProperAncestorFrame(nsIFrame* aTarget);
-
-  /**
-   * @return the nearest async scrollable ancestor frame of @aTarget, excluding
-   * @aTarget itself. If there is no async scrollable ancestor frame, falls back
-   * to the root frame.
-   */
-  static nsIFrame* GetAsyncScrollableProperAncestorFrameOrFallback(nsIFrame* aTarget);
-
   /**
    * Sets a zero margin display port on all proper ancestors of aFrame that
    * are async scrollable.