--- a/dom/animation/CSSPseudoElement.cpp
+++ b/dom/animation/CSSPseudoElement.cpp
@@ -31,16 +31,22 @@ CSSPseudoElement::~CSSPseudoElement()
 {
   // Element might have been unlinked already, so we have to do null check.
   if (mParentElement) {
     mParentElement->DeleteProperty(
       GetCSSPseudoElementPropertyAtom(mPseudoType));
   }
 }
 
+ParentObject
+CSSPseudoElement::GetParentObject() const
+{
+  return mParentElement->GetParentObject();
+}
+
 JSObject*
 CSSPseudoElement::WrapObject(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
 {
   return CSSPseudoElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
 void
 CSSPseudoElement::GetAnimations(nsTArray<RefPtr<Animation>>& aRetVal)

--- a/dom/animation/CSSPseudoElement.h
+++ b/dom/animation/CSSPseudoElement.h
@@ -27,20 +27,17 @@ class CSSPseudoElement final : public ns
 public:
   NS_INLINE_DECL_CYCLE_COLLECTING_NATIVE_REFCOUNTING(CSSPseudoElement)
   NS_DECL_CYCLE_COLLECTION_SCRIPT_HOLDER_NATIVE_CLASS(CSSPseudoElement)
 
 protected:
   virtual ~CSSPseudoElement();
 
 public:
-  ParentObject GetParentObject() const
-  {
-    return mParentElement->GetParentObject();
-  }
+  ParentObject GetParentObject() const;
 
   virtual JSObject* WrapObject(JSContext* aCx,
                                JS::Handle<JSObject*> aGivenProto) override;
 
   nsCSSPseudoElements::Type GetType() const { return mPseudoType; }
   void GetType(nsString& aRetVal) const
   {
     MOZ_ASSERT(nsCSSPseudoElements::GetPseudoAtom(mPseudoType),