Web Animations: Use StringKeyframes for element.animate()

Source/core/animation/Keyframe.h

Index: Source/core/animation/Keyframe.h
diff --git a/Source/core/animation/Keyframe.h b/Source/core/animation/Keyframe.h
index 8b2075771b1105e935dfc0fbbe4da98441fd3ef5..2449894ee01b6da64bb4b1e21c59f1ef73154601 100644
--- a/Source/core/animation/Keyframe.h
+++ b/Source/core/animation/Keyframe.h
@@ -13,6 +13,8 @@ namespace WebCore {
 
 typedef HashSet<CSSPropertyID> PropertySet;
 
+class Element;
+
 // FIXME: Make Keyframe immutable
 class Keyframe : public RefCountedWillBeGarbageCollectedFinalized<Keyframe> {
 public:
@@ -55,7 +57,7 @@ public:
         virtual bool isStringPropertySpecificKeyframe() const { return false; }
 
         virtual PassOwnPtrWillBeRawPtr<PropertySpecificKeyframe> neutralKeyframe(double offset, PassRefPtr<TimingFunction> easing) const = 0;
-        virtual PassRefPtrWillBeRawPtr<Interpolation> createInterpolation(CSSPropertyID, WebCore::Keyframe::PropertySpecificKeyframe* end) const = 0;
+        virtual PassRefPtrWillBeRawPtr<Interpolation> createInterpolation(CSSPropertyID, WebCore::Keyframe::PropertySpecificKeyframe* end, Element*) const = 0;
 
         virtual void trace(Visitor*) = 0;