[Oilpan] Migrate most classes under core/animations to Oilpan heap.

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 260f0b42cec57f52e8b66b0dcfd7d7537a176282..c009293faf685005dfe6966be1212b0a114d8536 100644
--- a/Source/core/animation/animatable/AnimatableImage.h
+++ b/Source/core/animation/animatable/AnimatableImage.h
@@ -40,9 +40,9 @@ namespace blink {
 class AnimatableImage final : public AnimatableValue {
 public:
     virtual ~AnimatableImage() { }
-    static PassRefPtrWillBeRawPtr<AnimatableImage> create(PassRefPtrWillBeRawPtr<CSSValue> value)
+    static AnimatableImage* create(PassRefPtrWillBeRawPtr<CSSValue> value)
     {
-        return adoptRefWillBeNoop(new AnimatableImage(value));
+        return new AnimatableImage(value);
     }
     CSSValue* toCSSValue() const { return m_value.get(); }
 
@@ -53,7 +53,7 @@ public:
     }
 
 protected:
-    virtual PassRefPtrWillBeRawPtr<AnimatableValue> interpolateTo(const AnimatableValue*, double fraction) const override;
+    virtual AnimatableValue* interpolateTo(const AnimatableValue*, double fraction) const override;
     virtual bool usesDefaultInterpolationWith(const AnimatableValue*) const override;
 
 private: