Web Animations: Fix Player's timing update when source content becomes longer

Source/core/animation/AnimationPlayer.h

Index: Source/core/animation/AnimationPlayer.h
diff --git a/Source/core/animation/AnimationPlayer.h b/Source/core/animation/AnimationPlayer.h
index 0cf77a91eaaf5a8c386015e0189fe5e7af756979..16b46f2b3581eebc2b103cf1e089c80901b4c347 100644
--- a/Source/core/animation/AnimationPlayer.h
+++ b/Source/core/animation/AnimationPlayer.h
@@ -82,6 +82,7 @@ public:
     void setCurrentTime(double newCurrentTime);
 
     double currentTimeInternal() const;
+    double unlimitedCurrentTimeInternal() const;
 
     void setCurrentTimeInternal(double newCurrentTime, TimingUpdateReason = TimingUpdateOnDemand);
     bool paused() const { return m_paused && !m_isPausedForTesting; }