Ensure baseComputedStyle optimisation is cleared during registered custom property animations

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

Index: third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
index ac4174a99979dee637be416d28c072496aeea7dd..2fb0f4d37bf4fae17a2444dab37f935129d109b3 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -612,12 +612,17 @@ static const ComputedStyle* calculateBaseComputedStyle(
 
 static void updateBaseComputedStyle(StyleResolverState& state,
                                     Element* animatingElement) {
-  if (!animatingElement || state.isAnimatingCustomProperties())
+  if (!animatingElement)
     return;
 
   ElementAnimations* elementAnimations = animatingElement->elementAnimations();
-  if (elementAnimations)
-    elementAnimations->updateBaseComputedStyle(state.style());
+  if (elementAnimations) {
+    if (state.isAnimatingCustomProperties()) {
+      elementAnimations->clearBaseComputedStyle();
+    } else {
+      elementAnimations->updateBaseComputedStyle(state.style());
+    }
+  }
 }
 
 PassRefPtr<ComputedStyle> StyleResolver::styleForElement(