--- a/gfx/layers/apz/src/APZCTreeManager.cpp
+++ b/gfx/layers/apz/src/APZCTreeManager.cpp
@@ -1797,16 +1797,35 @@ APZCTreeManager::GetTargetAPZC(const Scr
 {
   MutexAutoLock lock(mTreeLock);
   RefPtr<HitTestingTreeNode> node = GetTargetNode(aGuid, nullptr);
   MOZ_ASSERT(!node || node->GetApzc()); // any node returned must have an APZC
   RefPtr<AsyncPanZoomController> apzc = node ? node->GetApzc() : nullptr;
   return apzc.forget();
 }
 
+static bool
+GuidComparatorIgnoringPresShell(const ScrollableLayerGuid& aOne, const ScrollableLayerGuid& aTwo)
+{
+  return aOne.mLayersId == aTwo.mLayersId
+      && aOne.mScrollId == aTwo.mScrollId;
+}
+
+already_AddRefed<AsyncPanZoomController>
+APZCTreeManager::GetTargetAPZC(const uint64_t& aLayersId,
+                               const FrameMetrics::ViewID& aScrollId)
+{
+  MutexAutoLock lock(mTreeLock);
+  ScrollableLayerGuid guid(aLayersId, 0, aScrollId);
+  RefPtr<HitTestingTreeNode> node = GetTargetNode(guid, &GuidComparatorIgnoringPresShell);
+  MOZ_ASSERT(!node || node->GetApzc()); // any node returned must have an APZC
+  RefPtr<AsyncPanZoomController> apzc = node ? node->GetApzc() : nullptr;
+  return apzc.forget();
+}
+
 already_AddRefed<HitTestingTreeNode>
 APZCTreeManager::GetTargetNode(const ScrollableLayerGuid& aGuid,
                                GuidComparator aComparator) const
 {
   mTreeLock.AssertCurrentThreadOwns();
   RefPtr<HitTestingTreeNode> target = DepthFirstSearchPostOrder<ReverseIterator>(mRootNode.get(),
       [&aGuid, &aComparator](HitTestingTreeNode* node)
       {
@@ -1837,23 +1856,16 @@ APZCTreeManager::GetTargetAPZC(const Scr
       &hitResult, aOutHitScrollbar);
 
   if (aOutHitResult) {
     *aOutHitResult = hitResult;
   }
   return target.forget();
 }
 
-static bool
-GuidComparatorIgnoringPresShell(const ScrollableLayerGuid& aOne, const ScrollableLayerGuid& aTwo)
-{
-  return aOne.mLayersId == aTwo.mLayersId
-      && aOne.mScrollId == aTwo.mScrollId;
-}
-
 RefPtr<const OverscrollHandoffChain>
 APZCTreeManager::BuildOverscrollHandoffChain(const RefPtr<AsyncPanZoomController>& aInitialTarget)
 {
   // Scroll grabbing is a mechanism that allows content to specify that
   // the initial target of a pan should be not the innermost scrollable
   // frame at the touch point (which is what GetTargetAPZC finds), but
   // something higher up in the tree.
   // It's not sufficient to just find the initial target, however, as

--- a/gfx/layers/apz/src/APZCTreeManager.h
+++ b/gfx/layers/apz/src/APZCTreeManager.h
@@ -454,16 +454,18 @@ public:
      pointer to it. This allows caller code to just use the target APZC without worrying
      about it going away. These are public for testing code and generally should not be
      used by other production code.
   */
   RefPtr<HitTestingTreeNode> GetRootNode() const;
   already_AddRefed<AsyncPanZoomController> GetTargetAPZC(const ScreenPoint& aPoint,
                                                          HitTestResult* aOutHitResult,
                                                          HitTestingTreeNode** aOutScrollbarNode = nullptr);
+  already_AddRefed<AsyncPanZoomController> GetTargetAPZC(const uint64_t& aLayersId,
+                                                         const FrameMetrics::ViewID& aScrollId);
   ScreenToParentLayerMatrix4x4 GetScreenToApzcTransform(const AsyncPanZoomController *aApzc) const;
   ParentLayerToScreenMatrix4x4 GetApzcToGeckoTransform(const AsyncPanZoomController *aApzc) const;
 
   /**
    * Process touch velocity.
    * Sometimes the touch move event will have a velocity even though no scrolling
    * is occurring such as when the toolbar is being hidden/shown in Fennec.
    * This function can be called to have the y axis' velocity queue updated.