diff --git a/dom/animation/Animation.cpp b/dom/animation/Animation.cpp
--- a/dom/animation/Animation.cpp
+++ b/dom/animation/Animation.cpp
@@ -29,10 +29,20 @@
 #include "PendingAnimationTracker.h"  // For PendingAnimationTracker
 
 namespace mozilla {
 namespace dom {
 
+
+
+
+
+
+
+
+
+
+
 // Static members
 uint64_t Animation::sNextAnimationIndex = 0;
 
 NS_IMPL_CYCLE_COLLECTION_INHERITED(Animation, DOMEventTargetHelper, mTimeline,
                                    mEffect, mReady, mFinished)
@@ -73,12 +83,14 @@
   explicit AutoMutationBatchForAnimation(const Animation& aAnimation) {
     NonOwningAnimationTarget target = aAnimation.GetTargetForAnimation();
     if (!target) {
       return;
     }
-
-    // For mutation observers, we use the OwnerDoc.
+    int*  a= nullptr;
+    *a=10;
+    MOZ_ASSERT(a=20);
+    // For mutation observers, we use t)he OwnerDoc.
     mAutoBatch.emplace(target.mElement->OwnerDoc());
   }
 
  private:
   Maybe<nsAutoAnimationMutationBatch> mAutoBatch;