diff --git a/dom/animation/AnimationPlayer.h b/dom/animation/AnimationPlayer.h
index de652b23956..c4f3ac884e8 100644
--- a/dom/animation/AnimationPlayer.h
+++ b/dom/animation/AnimationPlayer.h
@@ -35,9 +35,9 @@ protected:
 
 public:
   explicit AnimationPlayer(AnimationTimeline* aTimeline)
-    : mIsRunningOnCompositor(false)
-    , mTimeline(aTimeline)
+    : mTimeline(aTimeline)
     , mIsPaused(false)
+    , mIsRunningOnCompositor(false)
   {
   }
 
@@ -92,6 +92,9 @@ public:
     return GetSource() && GetSource()->IsInEffect();
   }
 
+  void SetIsRunningOnCompositor() { mIsRunningOnCompositor = true; }
+  void ClearIsRunningOnCompositor() { mIsRunningOnCompositor = false; }
+
   // Returns true if this animation does not currently need to update
   // style on the main thread (e.g. because it is empty, or is
   // running on the compositor).
@@ -99,7 +102,6 @@ public:
 
   // The beginning of the delay period.
   Nullable<TimeDuration> mStartTime; // Timeline timescale
-  bool mIsRunningOnCompositor;
 
   nsRefPtr<AnimationTimeline> mTimeline;
   nsRefPtr<Animation> mSource;
@@ -111,6 +113,7 @@ protected:
 
   Nullable<TimeDuration> mHoldTime;  // Player timescale
   bool mIsPaused;
+  bool mIsRunningOnCompositor;
 };
 
 } // namespace dom
diff --git a/layout/base/nsDisplayList.cpp b/layout/base/nsDisplayList.cpp
index c258b35828d..7f3db0a27fe 100644
--- a/layout/base/nsDisplayList.cpp
+++ b/layout/base/nsDisplayList.cpp
@@ -412,7 +412,7 @@ AddAnimationsForProperty(nsIFrame* aFrame, nsCSSProperty aProperty,
       continue;
     }
     AddAnimationForProperty(aFrame, aProperty, player, aLayer, aData, aPending);
-    player->mIsRunningOnCompositor = true;
+    player->SetIsRunningOnCompositor();
   }
 }
 
diff --git a/layout/style/nsAnimationManager.cpp b/layout/style/nsAnimationManager.cpp
index 322a5b7105b..352b991abca 100644
--- a/layout/style/nsAnimationManager.cpp
+++ b/layout/style/nsAnimationManager.cpp
@@ -311,7 +311,7 @@ nsAnimationManager::CheckAnimationRule(nsStyleContext* aStyleContext,
           }
 
           // Reset compositor state so animation will be re-synchronized.
-          oldPlayer->mIsRunningOnCompositor = false;
+          oldPlayer->ClearIsRunningOnCompositor();
 
           // Handle changes in play state.
           // CSSAnimationPlayer takes care of override behavior so that,
diff --git a/layout/style/nsTransitionManager.cpp b/layout/style/nsTransitionManager.cpp
index 20eb9aeea54..19da9324a65 100644
--- a/layout/style/nsTransitionManager.cpp
+++ b/layout/style/nsTransitionManager.cpp
@@ -834,7 +834,7 @@ nsTransitionManager::FlushTransitions(FlushFlags aFlags)
           } else if ((computedTiming.mPhase ==
                       ComputedTiming::AnimationPhase_Active) &&
                      canThrottleTick &&
-                    !player->mIsRunningOnCompositor) {
+                     !player->IsRunningOnCompositor()) {
             // Start a transition with a delay where we should start the
             // transition proper.
             collection->UpdateAnimationGeneration(mPresContext);