--- a/gfx/layers/wr/WebRenderScrollData.cpp
+++ b/gfx/layers/wr/WebRenderScrollData.cpp
@@ -18,17 +18,16 @@
 namespace mozilla {
 namespace layers {
 
 WebRenderLayerScrollData::WebRenderLayerScrollData()
   : mDescendantCount(-1)
   , mTransformIsPerspective(false)
   , mEventRegionsOverride(EventRegionsOverride::NoOverride)
   , mScrollbarAnimationId(0)
-  , mScrollbarTargetContainerId(FrameMetrics::NULL_SCROLL_ID)
   , mFixedPosScrollContainerId(FrameMetrics::NULL_SCROLL_ID)
 {
 }
 
 WebRenderLayerScrollData::~WebRenderLayerScrollData()
 {
 }
 
@@ -120,18 +119,16 @@ WebRenderLayerScrollData::Dump(const Web
     Stringify(mVisibleRegion).c_str());
   printf_stderr("  event regions: %s override: 0x%x\n",
     Stringify(mEventRegions).c_str(), mEventRegionsOverride);
   if (mReferentId) {
     printf_stderr("  ref layers id: 0x%" PRIx64 "\n", uint64_t(*mReferentId));
   }
   //printf_stderr("  scroll thumb: %s animation: %" PRIu64 "\n",
   //  Stringify(mScrollThumbData).c_str(), mScrollbarAnimationId);
-  printf_stderr("  scroll container: %d target: %" PRIu64 "\n",
-    mScrollbarContainerDirection.isSome(), mScrollbarTargetContainerId);
   printf_stderr("  fixed pos container: %" PRIu64 "\n",
     mFixedPosScrollContainerId);
 }
 
 WebRenderScrollData::WebRenderScrollData()
   : mManager(nullptr)
   , mIsFirstPaint(false)
   , mPaintSequenceNumber(0)

--- a/gfx/layers/wr/WebRenderScrollData.h
+++ b/gfx/layers/wr/WebRenderScrollData.h
@@ -76,20 +76,16 @@ public:
   const LayerIntRegion& GetVisibleRegion() const { return mVisibleRegion; }
   void SetReferentId(LayersId aReferentId) { mReferentId = Some(aReferentId); }
   Maybe<LayersId> GetReferentId() const { return mReferentId; }
 
   void SetScrollbarData(const ScrollbarData& aData) { mScrollbarData = aData; }
   const ScrollbarData& GetScrollbarData() const { return mScrollbarData; }
   void SetScrollbarAnimationId(const uint64_t& aId) { mScrollbarAnimationId = aId; }
   const uint64_t& GetScrollbarAnimationId() const { return mScrollbarAnimationId; }
-  void SetScrollbarTargetContainerId(FrameMetrics::ViewID aId) { mScrollbarTargetContainerId = aId; }
-  FrameMetrics::ViewID GetScrollbarTargetContainerId() const { return mScrollbarTargetContainerId; }
-  void SetScrollbarContainerDirection(ScrollDirection aDirection) { mScrollbarContainerDirection = Some(aDirection); }
-  Maybe<ScrollDirection> GetScrollbarContainerDirection() const { return mScrollbarContainerDirection; }
 
   void SetFixedPositionScrollContainerId(FrameMetrics::ViewID aId) { mFixedPosScrollContainerId = aId; }
   FrameMetrics::ViewID GetFixedPositionScrollContainerId() const { return mFixedPosScrollContainerId; }
 
   void Dump(const WebRenderScrollData& aOwner) const;
 
   friend struct IPC::ParamTraits<WebRenderLayerScrollData>;
 
@@ -112,18 +108,16 @@ private:
   gfx::Matrix4x4 mTransform;
   bool mTransformIsPerspective;
   EventRegions mEventRegions;
   LayerIntRegion mVisibleRegion;
   Maybe<LayersId> mReferentId;
   EventRegionsOverride mEventRegionsOverride;
   ScrollbarData mScrollbarData;
   uint64_t mScrollbarAnimationId;
-  FrameMetrics::ViewID mScrollbarTargetContainerId;
-  Maybe<ScrollDirection> mScrollbarContainerDirection;
   FrameMetrics::ViewID mFixedPosScrollContainerId;
 };
 
 // Data needed by APZ, for the whole layer tree. One instance of this class
 // is created for each transaction sent over PWebRenderBridge. It is populated
 // with information from the WebRender layer tree on the client side and the
 // information is used by APZ on the parent side.
 class WebRenderScrollData
@@ -225,36 +219,32 @@ struct ParamTraits<mozilla::layers::WebR
     WriteParam(aMsg, aParam.mTransform);
     WriteParam(aMsg, aParam.mTransformIsPerspective);
     WriteParam(aMsg, aParam.mEventRegions);
     WriteParam(aMsg, aParam.mVisibleRegion);
     WriteParam(aMsg, aParam.mReferentId);
     WriteParam(aMsg, aParam.mEventRegionsOverride);
     WriteParam(aMsg, aParam.mScrollbarData);
     WriteParam(aMsg, aParam.mScrollbarAnimationId);
-    WriteParam(aMsg, aParam.mScrollbarTargetContainerId);
-    WriteParam(aMsg, aParam.mScrollbarContainerDirection);
     WriteParam(aMsg, aParam.mFixedPosScrollContainerId);
   }
 
   static bool
   Read(const Message* aMsg, PickleIterator* aIter, paramType* aResult)
   {
     return ReadParam(aMsg, aIter, &aResult->mDescendantCount)
         && ReadParam(aMsg, aIter, &aResult->mScrollIds)
         && ReadParam(aMsg, aIter, &aResult->mTransform)
         && ReadParam(aMsg, aIter, &aResult->mTransformIsPerspective)
         && ReadParam(aMsg, aIter, &aResult->mEventRegions)
         && ReadParam(aMsg, aIter, &aResult->mVisibleRegion)
         && ReadParam(aMsg, aIter, &aResult->mReferentId)
         && ReadParam(aMsg, aIter, &aResult->mEventRegionsOverride)
         && ReadParam(aMsg, aIter, &aResult->mScrollbarData)
         && ReadParam(aMsg, aIter, &aResult->mScrollbarAnimationId)
-        && ReadParam(aMsg, aIter, &aResult->mScrollbarTargetContainerId)
-        && ReadParam(aMsg, aIter, &aResult->mScrollbarContainerDirection)
         && ReadParam(aMsg, aIter, &aResult->mFixedPosScrollContainerId);
   }
 };
 
 template<>
 struct ParamTraits<mozilla::layers::WebRenderScrollData>
 {
   typedef mozilla::layers::WebRenderScrollData paramType;

--- a/gfx/layers/wr/WebRenderScrollDataWrapper.h
+++ b/gfx/layers/wr/WebRenderScrollDataWrapper.h
@@ -298,23 +298,26 @@ public:
   {
     MOZ_ASSERT(IsValid());
     return mLayer->GetScrollbarAnimationId();
   }
 
   FrameMetrics::ViewID GetScrollbarTargetContainerId() const
   {
     MOZ_ASSERT(IsValid());
-    return mLayer->GetScrollbarTargetContainerId();
+    return mLayer->GetScrollbarData().mTargetViewId;
   }
 
   Maybe<ScrollDirection> GetScrollbarContainerDirection() const
   {
     MOZ_ASSERT(IsValid());
-    return mLayer->GetScrollbarContainerDirection();
+    const ScrollbarData& data = mLayer->GetScrollbarData();
+    return (data.mScrollbarLayerType == ScrollbarLayerType::Container)
+        ? data.mDirection
+        : Nothing();
   }
 
   FrameMetrics::ViewID GetFixedPositionScrollContainerId() const
   {
     MOZ_ASSERT(IsValid());
     return mLayer->GetFixedPositionScrollContainerId();
   }
 

--- a/layout/painting/nsDisplayList.cpp
+++ b/layout/painting/nsDisplayList.cpp
@@ -7041,27 +7041,25 @@ nsDisplayOwnLayer::UpdateScrollData(mozi
                                     mozilla::layers::WebRenderLayerScrollData* aLayerData)
 {
   bool ret = false;
   if (IsScrollThumbLayer()) {
     ret = true;
     if (aLayerData) {
       aLayerData->SetScrollbarData(mScrollbarData);
       aLayerData->SetScrollbarAnimationId(mWrAnimationId);
-      aLayerData->SetScrollbarTargetContainerId(mScrollbarData.mTargetViewId);
-    }
-  }
-  if (mFlags & nsDisplayOwnLayerFlags::eScrollbarContainer) {
+    }
+  } else if (mFlags & nsDisplayOwnLayerFlags::eScrollbarContainer) {
     ret = true;
     if (aLayerData) {
-      ScrollDirection dir = (mFlags & nsDisplayOwnLayerFlags::eVerticalScrollbar)
-                          ? ScrollDirection::eVertical
-                          : ScrollDirection::eHorizontal;
-      aLayerData->SetScrollbarContainerDirection(dir);
-      aLayerData->SetScrollbarTargetContainerId(mScrollbarData.mTargetViewId);
+      mScrollbarData.mScrollbarLayerType = ScrollbarLayerType::Container;
+      mScrollbarData.mDirection = (mFlags & nsDisplayOwnLayerFlags::eVerticalScrollbar)
+                                  ? Some(ScrollDirection::eVertical)
+                                  : Some(ScrollDirection::eHorizontal);
+      aLayerData->SetScrollbarData(mScrollbarData);
     }
   }
   return ret;
 }
 
 void
 nsDisplayOwnLayer::WriteDebugInfo(std::stringstream& aStream)
 {