--- a/gfx/layers/composite/AsyncCompositionManager.cpp
+++ b/gfx/layers/composite/AsyncCompositionManager.cpp
@@ -640,16 +640,56 @@ ApplyAnimatedValue(Layer* aLayer,
                                  transformData);
       break;
     }
     default:
       MOZ_ASSERT_UNREACHABLE("Unhandled animated property");
   }
 }
 
+static uint64_t
+LayersIdFor(Layer* aLayer)
+{
+  Layer* layer = aLayer;
+  while (layer) {
+    if (layer->AsRefLayer()) {
+      return layer->AsRefLayer()->GetReferentId();
+    }
+    layer = layer->GetParent();
+  }
+
+  // Return the root layer tree ID.
+  if (LayerManager* manager = aLayer->Manager()) {
+    if (Compositor* compositor = manager->AsLayerManagerComposite()->GetCompositor()) {
+      if (CompositorBridgeParent* parent = compositor->GetCompositorBridgeParent()) {
+        return parent->RootLayerTreeId();
+      }
+    }
+  }
+  return 0;
+}
+
+static AsyncPanZoomController*
+FindAPZC(LayerMetricsWrapper aRoot, uint64_t aLayersId, FrameMetrics::ViewID aViewId)
+{
+  LayerMetricsWrapper result = DepthFirstSearch<ForwardIterator>(
+      aRoot,
+      [aLayersId, aViewId] (LayerMetricsWrapper aLayer)
+      {
+        if (AsyncPanZoomController* apzc = aLayer.GetApzc()) {
+          ScrollableLayerGuid guid = apzc->GetGuid();
+          if (guid.mLayersId == aLayersId && guid.mScrollId == aViewId) {
+            return true;
+          }
+        }
+        return false;
+      });
+  return result.IsValid() ? result.GetApzc() : nullptr;
+}
+
 static bool
 SampleAnimations(Layer* aLayer,
                  CompositorAnimationStorage* aStorage,
                  TimeStamp aPoint,
                  uint64_t* aLayerAreaAnimated)
 {
   bool activeAnimations = false;