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

Source/core/animation/ConstantStyleInterpolation.h

Index: Source/core/animation/ConstantStyleInterpolation.h
diff --git a/Source/core/animation/ConstantStyleInterpolation.h b/Source/core/animation/ConstantStyleInterpolation.h
index 0ccda69bf72f08c69bc0f19dec04885dd2aac50f..596d8e56fb78a99f45bbcc5494ab2aa36a4c1088 100644
--- a/Source/core/animation/ConstantStyleInterpolation.h
+++ b/Source/core/animation/ConstantStyleInterpolation.h
@@ -12,9 +12,9 @@ namespace blink {
 
 class ConstantStyleInterpolation : public StyleInterpolation {
 public:
-    static PassRefPtrWillBeRawPtr<ConstantStyleInterpolation> create(CSSValue* value, CSSPropertyID id)
+    static ConstantStyleInterpolation* create(CSSValue* value, CSSPropertyID id)
     {
-        return adoptRefWillBeNoop(new ConstantStyleInterpolation(value, id));
+        return new ConstantStyleInterpolation(value, id);
     }
 
     void apply(StyleResolverState& state) const override