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

Source/core/animation/animatable/AnimatableUnknown.h

Index: Source/core/animation/animatable/AnimatableUnknown.h
diff --git a/Source/core/animation/animatable/AnimatableUnknown.h b/Source/core/animation/animatable/AnimatableUnknown.h
index 8105550ecd0849e6445623c289ab67246c4803b4..37563a2247451695d731a19f70808895cf05e2cf 100644
--- a/Source/core/animation/animatable/AnimatableUnknown.h
+++ b/Source/core/animation/animatable/AnimatableUnknown.h
@@ -41,13 +41,13 @@ class AnimatableUnknown final : public AnimatableValue {
 public:
     ~AnimatableUnknown() override { }
 
-    static PassRefPtrWillBeRawPtr<AnimatableUnknown> create(PassRefPtrWillBeRawPtr<CSSValue> value)
+    static AnimatableUnknown* create(PassRefPtrWillBeRawPtr<CSSValue> value)
     {
-        return adoptRefWillBeNoop(new AnimatableUnknown(value));
+        return new AnimatableUnknown(value);
     }
-    static PassRefPtrWillBeRawPtr<AnimatableUnknown> create(CSSValueID value)
+    static AnimatableUnknown* create(CSSValueID value)
     {
-        return adoptRefWillBeNoop(new AnimatableUnknown(cssValuePool().createIdentifierValue(value)));
+        return new AnimatableUnknown(cssValuePool().createIdentifierValue(value));
     }
 
     PassRefPtrWillBeRawPtr<CSSValue> toCSSValue() const { return m_value; }
@@ -60,7 +60,7 @@ public:
     }
 
 protected:
-    PassRefPtrWillBeRawPtr<AnimatableValue> interpolateTo(const AnimatableValue* value, double fraction) const override
+    AnimatableValue* interpolateTo(const AnimatableValue* value, double fraction) const override
     {
         return defaultInterpolateTo(this, value, fraction);
     }