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

Source/core/animation/animatable/AnimatableVisibility.h

Index: Source/core/animation/animatable/AnimatableVisibility.h
diff --git a/Source/core/animation/animatable/AnimatableVisibility.h b/Source/core/animation/animatable/AnimatableVisibility.h
index f52993467de9360e27a55604dcfa3f4e92680845..e9c4c57f263d2e01680be3471fed3c4a24d466a1 100644
--- a/Source/core/animation/animatable/AnimatableVisibility.h
+++ b/Source/core/animation/animatable/AnimatableVisibility.h
@@ -40,9 +40,9 @@ namespace blink {
 class CORE_EXPORT AnimatableVisibility final : public AnimatableValue {
 public:
     ~AnimatableVisibility() override { }
-    static PassRefPtrWillBeRawPtr<AnimatableVisibility> create(EVisibility visibility)
+    static AnimatableVisibility* create(EVisibility visibility)
     {
-        return adoptRefWillBeNoop(new AnimatableVisibility(visibility));
+        return new AnimatableVisibility(visibility);
     }
 
     EVisibility visibility() const { return m_visibility; }
@@ -50,7 +50,7 @@ public:
     DEFINE_INLINE_VIRTUAL_TRACE() { AnimatableValue::trace(visitor); }
 
 protected:
-    PassRefPtrWillBeRawPtr<AnimatableValue> interpolateTo(const AnimatableValue*, double fraction) const override;
+    AnimatableValue* interpolateTo(const AnimatableValue*, double fraction) const override;
     bool usesDefaultInterpolationWith(const AnimatableValue*) const override;
 
 private: