CSSValue Immediates: Replace CSSPrimitiveValue usage with const references

Source/core/animation/animatable/AnimatableImage.h

Index: Source/core/animation/animatable/AnimatableImage.h
diff --git a/Source/core/animation/animatable/AnimatableImage.h b/Source/core/animation/animatable/AnimatableImage.h
index 9914b8d378226936dd477dd24b130af20fb974d5..d7d7b283ae427ec4802e05f5a0dba662f1c8f28d 100644
--- a/Source/core/animation/animatable/AnimatableImage.h
+++ b/Source/core/animation/animatable/AnimatableImage.h
@@ -40,11 +40,11 @@ namespace blink {
 class AnimatableImage final : public AnimatableValue {
 public:
     virtual ~AnimatableImage() { }
-    static PassRefPtrWillBeRawPtr<AnimatableImage> create(CSSValue value)
+    static PassRefPtrWillBeRawPtr<AnimatableImage> create(const CSSValue& value)
     {
         return adoptRefWillBeNoop(new AnimatableImage(value));
     }
-    CSSValue toCSSValue() const { return m_value; }
+    const CSSValue& toCSSValue() const { return m_value; }
 
     DEFINE_INLINE_VIRTUAL_TRACE()
     {
@@ -57,7 +57,7 @@ protected:
     virtual bool usesDefaultInterpolationWith(const AnimatableValue*) const override;
 
 private:
-    AnimatableImage(CSSValue value)
+    AnimatableImage(const CSSValue& value)
         : m_value(value)
     {
     }