Web Animations API: Deferred computation of interpolated values

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 f61533391b5c2cccaf6d0c2106df01942a2a1bad..be6757f5e23ef984c9abd521a36b8d6fe8cb6ce5 100644
--- a/Source/core/animation/css/CSSAnimations.cpp
+++ b/Source/core/animation/css/CSSAnimations.cpp
@@ -36,6 +36,7 @@
 #include "core/animation/CompositorAnimations.h"
 #include "core/animation/DocumentTimeline.h"
 #include "core/animation/KeyframeEffectModel.h"
+#include "core/animation/LegacyStyleInterpolation.h"
 #include "core/animation/css/CSSAnimatableValueFactory.h"
 #include "core/animation/css/CSSAnimationDataList.h"
 #include "core/animation/css/CSSPropertyEquality.h"
@@ -442,6 +443,7 @@ void CSSAnimations::maybeApplyPendingUpdate(Element* element)
             OwnPtrWillBeRawPtr<WillBeHeapVector<RefPtrWillBeMember<Interpolation> > > sample = inertAnimationForSampling->sample(inheritedTime);
             ASSERT(sample->size() == 1);
             newFrames[0]->setPropertyValue(id, toLegacyStyleInterpolation(sample->at(0).get())->currentValue());
+            ASSERT(newFrames[0]->propertyValue(id));
 
             effect = AnimatableValueKeyframeEffectModel::create(newFrames);
         }