Web Animations CSS: Record if style recalc is for animation

Source/core/animation/css/CSSAnimations.cpp

Index: Source/core/animation/css/CSSAnimations.cpp
diff --git a/Source/core/animation/css/CSSAnimations.cpp b/Source/core/animation/css/CSSAnimations.cpp
index eb0e21b4dc6d5d3e90b61d5bbac2b1aff0ad754e..bbde17ab9299673c8e97c9defdb58f48ebecf57d 100644
--- a/Source/core/animation/css/CSSAnimations.cpp
+++ b/Source/core/animation/css/CSSAnimations.cpp
@@ -519,22 +519,24 @@ void CSSAnimations::maybeApplyPendingUpdate(Element* element)
     }
 }
 
-void CSSAnimations::calculateTransitionUpdateForProperty(CSSPropertyID id, const CSSAnimationData* anim, const RenderStyle& oldStyle, const RenderStyle& style, const TransitionMap* activeTransitions, CSSAnimationUpdate* update)
+void CSSAnimations::calculateTransitionUpdateForProperty(CSSPropertyID id, const CSSAnimationData* anim, const RenderStyle& oldStyle, const RenderStyle& style, const TransitionMap* activeTransitions, CSSAnimationUpdate* update, const Element* element)
 {
-    if (CSSPropertyAnimation::propertiesEqual(id, &oldStyle, &style))
-        return;
-
-    RefPtr<AnimatableValue> to = CSSAnimatableValueFactory::create(id, style);
-
+    RefPtr<AnimatableValue> to;
     if (activeTransitions) {
         TransitionMap::const_iterator activeTransitionIter = activeTransitions->find(id);
         if (activeTransitionIter != activeTransitions->end()) {
+            to = CSSAnimatableValueFactory::create(id, style);
             const AnimatableValue* activeTo = activeTransitionIter->value.to;
             if (to->equals(activeTo))
                 return;
             update->cancelTransition(id);
+            ASSERT(!element->activeAnimations() || !element->activeAnimations()->isAnimationStyleChange());
         }
     }
+    if (CSSPropertyAnimation::propertiesEqual(id, &oldStyle, &style))
+        return;
+    if (!to)
+        to = CSSAnimatableValueFactory::create(id, style);
 
     RefPtr<AnimatableValue> from = CSSAnimatableValueFactory::create(id, oldStyle);
     // If we have multiple transitions on the same property, we will use the
@@ -565,6 +567,7 @@ void CSSAnimations::calculateTransitionUpdateForProperty(CSSPropertyID id, const
     timing.fillMode = Timing::FillModeBoth;
 
     update->startTransition(id, from.get(), to.get(), InertAnimation::create(effect, timing, isPaused));
+    ASSERT(!element->activeAnimations() || !element->activeAnimations()->isAnimationStyleChange());
 }
 
 void CSSAnimations::calculateTransitionUpdate(CSSAnimationUpdate* update, const Element* element, const RenderStyle& style)
@@ -572,10 +575,18 @@ void CSSAnimations::calculateTransitionUpdate(CSSAnimationUpdate* update, const
     ActiveAnimations* activeAnimations = element->activeAnimations();
     const TransitionMap* activeTransitions = activeAnimations ? &activeAnimations->cssAnimations().m_transitions : 0;
 
+#if ASSERT_DISABLED
+    // In release builds we avoid the cost of checking for new and interrupted transitions if the style recalc is due to animation.
+    const bool animationStyleRecalc = activeAnimations && activeAnimations->isAnimationStyleChange();
+#else
+    // In debug builds we verify that it would have been safe to avoid populating and testing listedProperties if the style recalc is due to animation.
+    const bool animationStyleRecalc = false;
+#endif
+
     BitArray<numCSSProperties> listedProperties;
     bool anyTransitionHadAnimateAll = false;
     const RenderObject* renderer = element->renderer();
-    if (style.display() != NONE && renderer && renderer->style() && style.transitions()) {
+    if (!animationStyleRecalc && style.display() != NONE && renderer && renderer->style() && style.transitions()) {
         const RenderStyle& oldStyle = *renderer->style();
 
         for (size_t i = 0; i < style.transitions()->size(); ++i) {
@@ -604,7 +615,7 @@ void CSSAnimations::calculateTransitionUpdate(CSSAnimationUpdate* update, const
                 // but this is a bit hard to do with the current applyMatchedProperties system.
                 if (!update->compositableValuesForAnimations().contains(id)
                     && (!activeAnimations || !activeAnimations->cssAnimations().m_previousCompositableValuesForAnimations.contains(id))) {
-                    calculateTransitionUpdateForProperty(id, anim, oldStyle, style, activeTransitions, update);
+                    calculateTransitionUpdateForProperty(id, anim, oldStyle, style, activeTransitions, update, element);
                 }
             }
         }
@@ -614,8 +625,10 @@ void CSSAnimations::calculateTransitionUpdate(CSSAnimationUpdate* update, const
         for (TransitionMap::const_iterator iter = activeTransitions->begin(); iter != activeTransitions->end(); ++iter) {
             const TimedItem* timedItem = iter->value.transition;
             CSSPropertyID id = iter->key;
-            if (timedItem->phase() == TimedItem::PhaseAfter || (!anyTransitionHadAnimateAll && !listedProperties.get(id)))
+            if (timedItem->phase() == TimedItem::PhaseAfter || (!anyTransitionHadAnimateAll && !animationStyleRecalc && !listedProperties.get(id))) {
+                ASSERT(timedItem->phase() == TimedItem::PhaseAfter || !(activeAnimations && activeAnimations->isAnimationStyleChange()));
                 update->cancelTransition(id);
+            }
         }
     }
 }