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

Source/core/animation/animatable/AnimatableDouble.h

Index: Source/core/animation/animatable/AnimatableDouble.h
diff --git a/Source/core/animation/animatable/AnimatableDouble.h b/Source/core/animation/animatable/AnimatableDouble.h
index 618d0f0da986387ae3d18bc873e7df3bb3fa0d86..bce4780f235c211bd62e89967b3475a12d65a476 100644
--- a/Source/core/animation/animatable/AnimatableDouble.h
+++ b/Source/core/animation/animatable/AnimatableDouble.h
@@ -40,9 +40,9 @@ class CORE_EXPORT AnimatableDouble final : public AnimatableValue {
 public:
     ~AnimatableDouble() override { }
 
-    static PassRefPtrWillBeRawPtr<AnimatableDouble> create(double number)
+    static AnimatableDouble* create(double number)
     {
-        return adoptRefWillBeNoop(new AnimatableDouble(number));
+        return new AnimatableDouble(number);
     }
 
     double toDouble() const { return m_number; }
@@ -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;
 
 private:
     AnimatableDouble(double number)