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

Source/core/animation/animatable/AnimatableLength.h

Index: Source/core/animation/animatable/AnimatableLength.h
diff --git a/Source/core/animation/animatable/AnimatableLength.h b/Source/core/animation/animatable/AnimatableLength.h
index d369e51065f46d8ab9e133ad4ca15c98c12f122a..693b809c9fe15746e8eaf0adde90f1cc82f7c15e 100644
--- a/Source/core/animation/animatable/AnimatableLength.h
+++ b/Source/core/animation/animatable/AnimatableLength.h
@@ -39,9 +39,9 @@ namespace blink {
 
 class CORE_EXPORT AnimatableLength final : public AnimatableValue {
 public:
-    static PassRefPtrWillBeRawPtr<AnimatableLength> create(const Length& length, float zoom)
+    static AnimatableLength* create(const Length& length, float zoom)
     {
-        return adoptRefWillBeNoop(new AnimatableLength(length, zoom));
+        return new AnimatableLength(length, zoom);
     }
     Length length(float zoom, ValueRange) const;
 
@@ -53,12 +53,12 @@ public:
     DEFINE_INLINE_VIRTUAL_TRACE() { AnimatableValue::trace(visitor); }
 
 protected:
-    virtual PassRefPtrWillBeRawPtr<AnimatableValue> interpolateTo(const AnimatableValue*, double fraction) const override;
+    virtual AnimatableValue* interpolateTo(const AnimatableValue*, double fraction) const override;
 
 private:
-    static PassRefPtrWillBeRawPtr<AnimatableLength> create(double pixels, double percent, bool hasPixels, bool hasPercent)
+    static AnimatableLength* create(double pixels, double percent, bool hasPixels, bool hasPercent)
     {
-        return adoptRefWillBeNoop(new AnimatableLength(pixels, percent, hasPixels, hasPercent));
+        return new AnimatableLength(pixels, percent, hasPixels, hasPercent);
     }
     AnimatableLength(const Length&, float zoom);
     AnimatableLength(double pixels, double percent, bool hasPixels, bool hasPercent)