--- a/dom/events/AnimationEvent.cpp
+++ b/dom/events/AnimationEvent.cpp
@@ -42,28 +42,28 @@ AnimationEvent::Constructor(const Global
 {
   nsCOMPtr<EventTarget> t = do_QueryInterface(aGlobal.GetAsSupports());
   RefPtr<AnimationEvent> e = new AnimationEvent(t, nullptr, nullptr);
   bool trusted = e->Init(t);
 
   e->InitEvent(aType, aParam.mBubbles, aParam.mCancelable);
 
   InternalAnimationEvent* internalEvent = e->mEvent->AsAnimationEvent();
-  internalEvent->animationName = aParam.mAnimationName;
+  internalEvent->mAnimationName = aParam.mAnimationName;
   internalEvent->elapsedTime = aParam.mElapsedTime;
   internalEvent->pseudoElement = aParam.mPseudoElement;
 
   e->SetTrusted(trusted);
   return e.forget();
 }
 
 NS_IMETHODIMP
 AnimationEvent::GetAnimationName(nsAString& aAnimationName)
 {
-  aAnimationName = mEvent->AsAnimationEvent()->animationName;
+  aAnimationName = mEvent->AsAnimationEvent()->mAnimationName;
   return NS_OK;
 }
 
 NS_IMETHODIMP
 AnimationEvent::GetElapsedTime(float* aElapsedTime)
 {
   *aElapsedTime = ElapsedTime();
   return NS_OK;

--- a/layout/style/nsAnimationManager.h
+++ b/layout/style/nsAnimationManager.h
@@ -41,17 +41,17 @@ struct AnimationEventInfo {
                      const TimeStamp& aTimeStamp,
                      dom::Animation* aAnimation)
     : mElement(aElement)
     , mAnimation(aAnimation)
     , mEvent(true, aMessage)
     , mTimeStamp(aTimeStamp)
   {
     // XXX Looks like nobody initialize WidgetEvent::time
-    mEvent.animationName = aAnimationName;
+    mEvent.mAnimationName = aAnimationName;
     mEvent.elapsedTime = aElapsedTime.ToSeconds();
     mEvent.pseudoElement =
       AnimationCollection<dom::CSSAnimation>::PseudoTypeAsString(aPseudoType);
   }
 
   // InternalAnimationEvent doesn't support copy-construction, so we need
   // to ourselves in order to work with nsTArray
   AnimationEventInfo(const AnimationEventInfo& aOther)

--- a/widget/ContentEvents.h
+++ b/widget/ContentEvents.h
@@ -298,26 +298,26 @@ public:
                "Duplicate() must be overridden by sub class");
     InternalAnimationEvent* result =
       new InternalAnimationEvent(false, mMessage);
     result->AssignAnimationEventData(*this, true);
     result->mFlags = mFlags;
     return result;
   }
 
-  nsString animationName;
+  nsString mAnimationName;
   float elapsedTime;
   nsString pseudoElement;
 
   void AssignAnimationEventData(const InternalAnimationEvent& aEvent,
                                 bool aCopyTargets)
   {
     AssignEventData(aEvent, aCopyTargets);
 
-    animationName = aEvent.animationName;
+    mAnimationName = aEvent.mAnimationName;
     elapsedTime = aEvent.elapsedTime;
     pseudoElement = aEvent.pseudoElement;
   }
 };
 
 /******************************************************************************
  * mozilla::InternalSVGZoomEvent
  ******************************************************************************/