Web Animations CSS: Support Animation of StyleImage and LengthBox

Source/core/animation/AnimatableValue.h

Index: Source/core/animation/AnimatableValue.h
diff --git a/Source/core/animation/AnimatableValue.h b/Source/core/animation/AnimatableValue.h
index 94a65d1caef94df4bc2935393142b5abff923e5e..ddc5f142bff3fc160026d01ce0ea1f7acc308992 100644
--- a/Source/core/animation/AnimatableValue.h
+++ b/Source/core/animation/AnimatableValue.h
@@ -48,6 +48,8 @@ public:
     // For noncommutative values read add(A, B) to mean the value A with B composed onto it.
     static PassRefPtr<AnimatableValue> add(const AnimatableValue*, const AnimatableValue*);
 
+    bool isImage() const { return m_type == TypeImage; }
+    bool isLengthBox() const { return m_type == TypeLengthBox; }
     bool isNumber() const { return m_type == TypeNumber; }
     bool isNeutral() const { return m_type == TypeNeutral; }
     bool isTransform() const { return m_type == TypeTransform; }
@@ -55,6 +57,8 @@ public:
 
 protected:
     enum AnimatableType {
+        TypeImage,
+        TypeLengthBox,
         TypeNeutral,
         TypeNumber,
         TypeTransform,