--- a/gfx/webrender_bindings/WebRenderAPI.cpp
+++ b/gfx/webrender_bindings/WebRenderAPI.cpp
@@ -739,22 +739,24 @@ DisplayListBuilder::PopScrollLayer()
 void
 DisplayListBuilder::PushClipAndScrollInfo(const layers::FrameMetrics::ViewID& aScrollId,
                                           const wr::WrClipId* aClipId)
 {
   WRDL_LOG("PushClipAndScroll s=%" PRIu64 " c=%s\n", aScrollId,
       aClipId ? Stringify(aClipId->id).c_str() : "none");
   wr_dp_push_clip_and_scroll_info(mWrState, aScrollId,
       aClipId ? &(aClipId->id) : nullptr);
+  mScrollIdStack.push_back(aScrollId);
 }
 
 void
 DisplayListBuilder::PopClipAndScrollInfo()
 {
   WRDL_LOG("PopClipAndScroll\n");
+  mScrollIdStack.pop_back();
   wr_dp_pop_clip_and_scroll_info(mWrState);
 }
 
 void
 DisplayListBuilder::PushRect(const wr::LayoutRect& aBounds,
                              const wr::LayoutRect& aClip,
                              const wr::ColorF& aColor)
 {
@@ -984,16 +986,25 @@ DisplayListBuilder::TopmostClipId()
 {
   if (mClipIdStack.empty()) {
     return Nothing();
   }
   return Some(mClipIdStack.back());
 }
 
 Maybe<layers::FrameMetrics::ViewID>
+DisplayListBuilder::TopmostScrollId()
+{
+  if (mScrollIdStack.empty()) {
+    return Nothing();
+  }
+  return Some(mScrollIdStack.back());
+}
+
+Maybe<layers::FrameMetrics::ViewID>
 DisplayListBuilder::ParentScrollIdFor(layers::FrameMetrics::ViewID aScrollId)
 {
   auto it = mScrollParents.find(aScrollId);
   return (it == mScrollParents.end() ? Nothing() : Some(it->second));
 }
 
 } // namespace wr
 } // namespace mozilla

--- a/gfx/webrender_bindings/WebRenderAPI.h
+++ b/gfx/webrender_bindings/WebRenderAPI.h
@@ -304,16 +304,18 @@ public:
                      const float& aSpreadRadius,
                      const float& aBorderRadius,
                      const wr::BoxShadowClipMode& aClipMode);
 
   // Returns the clip id that was most recently pushed with PushClip and that
   // has not yet been popped with PopClip. Return Nothing() if the clip stack
   // is empty.
   Maybe<wr::WrClipId> TopmostClipId();
+  // Same as TopmostClipId() but for scroll layers.
+  Maybe<layers::FrameMetrics::ViewID> TopmostScrollId();
   // Returns the scroll id that was pushed just before the given scroll id. This
   // function returns Nothing() if the given scrollid has not been encountered,
   // or if it is the rootmost scroll id (and therefore has no ancestor).
   Maybe<layers::FrameMetrics::ViewID> ParentScrollIdFor(layers::FrameMetrics::ViewID aScrollId);
 
   // Try to avoid using this when possible.
   wr::WrState* Raw() { return mWrState; }
 protected: