Web Animations CSS: Unfreeze AnimationClock if sampling timelines does not trigger style recalc

Source/core/animation/DocumentTimeline.cpp

Index: Source/core/animation/DocumentTimeline.cpp
diff --git a/Source/core/animation/DocumentTimeline.cpp b/Source/core/animation/DocumentTimeline.cpp
index 1681ef4a4b74a5b0b9319b25542fd1dad63b9062..a5d1979d50f99b8ad8e2f1201b7d91fee36717a1 100644
--- a/Source/core/animation/DocumentTimeline.cpp
+++ b/Source/core/animation/DocumentTimeline.cpp
@@ -86,14 +86,20 @@ void DocumentTimeline::serviceAnimations(double monotonicAnimationStartTime)
     m_document->animationClock().updateTime(monotonicAnimationStartTime);
 
     double timeToNextEffect = std::numeric_limits<double>::infinity();
-    double playerNextEffect;
+    bool didTriggerStyleRecalc = false;
     for (int i = m_players.size() - 1; i >= 0; --i) {
-        if (!m_players[i]->update(&playerNextEffect))
+        double playerNextEffect;
+        bool playerDidTriggerStyleRecalc;
+        if (!m_players[i]->update(&playerNextEffect, &playerDidTriggerStyleRecalc))
             m_players.remove(i);
+        didTriggerStyleRecalc |= playerDidTriggerStyleRecalc;
         if (playerNextEffect < timeToNextEffect)
             timeToNextEffect = playerNextEffect;
     }
 
+    if (!didTriggerStyleRecalc)
+        m_document->animationClock().unfreeze();
+
     if (!m_players.isEmpty()) {
         if (timeToNextEffect < s_minimumDelay)
             m_timing->serviceOnNextFrame();