Web Animations API: Deferred computation of interpolated values

Source/core/animation/StringKeyframe.h

Index: Source/core/animation/StringKeyframe.h
diff --git a/Source/core/animation/StringKeyframe.h b/Source/core/animation/StringKeyframe.h
index 7bf226e8cc74d0d20c977675bf70a7667169d84d..fbad2254076269ad7ccce5d234fe3f01a62059b7 100644
--- a/Source/core/animation/StringKeyframe.h
+++ b/Source/core/animation/StringKeyframe.h
@@ -5,6 +5,7 @@
 #ifndef StringKeyframe_h
 #define StringKeyframe_h
 
+#include "core/animation/InterpolableValuePromise.h"
 #include "core/animation/Keyframe.h"
 #include "core/css/StylePropertySet.h"
 
@@ -35,10 +36,7 @@ public:
         PropertySpecificKeyframe(double offset, PassRefPtr<TimingFunction> easing, CSSValue*, AnimationEffect::CompositeOperation);
 
         CSSValue* value() const { return m_value.get(); }
-        virtual const PassRefPtrWillBeRawPtr<AnimatableValue> getAnimatableValue() const OVERRIDE FINAL {
-            ASSERT(m_animatableValueCache);
-            return m_animatableValueCache.get();
-        }
+        virtual const PassRefPtrWillBeRawPtr<AnimatableValue> getAnimatableValue() const OVERRIDE FINAL;
 
         virtual PassOwnPtrWillBeRawPtr<Keyframe::PropertySpecificKeyframe> neutralKeyframe(double offset, PassRefPtr<TimingFunction> easing) const OVERRIDE FINAL;
         virtual PassRefPtrWillBeRawPtr<Interpolation> createInterpolation(CSSPropertyID, WebCore::Keyframe::PropertySpecificKeyframe* end, Element*) const OVERRIDE FINAL;
@@ -52,7 +50,7 @@ public:
         virtual bool isStringPropertySpecificKeyframe() const OVERRIDE { return true; }
 
         RefPtrWillBeMember<CSSValue> m_value;
-        mutable RefPtrWillBeMember<AnimatableValue> m_animatableValueCache;
+        mutable RefPtrWillBeMember<InterpolableValuePromise> m_interpolableValuePromiseCache;
     };
 
 private: