IDL: Generate union type containers

Source/core/animation/AnimationNodeTiming.h

Index: Source/core/animation/AnimationNodeTiming.h
diff --git a/Source/core/animation/AnimationNodeTiming.h b/Source/core/animation/AnimationNodeTiming.h
index d668936e34840bb5b33cdbff41565aed1cee8e4c..c81798bc165c4b0a23b60d56a987b578163d37ab 100644
--- a/Source/core/animation/AnimationNodeTiming.h
+++ b/Source/core/animation/AnimationNodeTiming.h
@@ -5,7 +5,6 @@
 #ifndef AnimationNodeTiming_h
 #define AnimationNodeTiming_h
 
-#include "bindings/core/v8/Nullable.h"
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "core/animation/AnimationNode.h"
 #include "wtf/RefCounted.h"
@@ -13,6 +12,8 @@
 
 namespace blink {
 
+class DoubleOrString;
+
 class AnimationNodeTiming : public RefCountedWillBeGarbageCollectedFinalized<AnimationNodeTiming>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
@@ -22,7 +23,7 @@ public:
     String fill();
     double iterationStart();
     double iterations();
-    void getDuration(String propertyName, Nullable<double>& element0, String& element1);
+    void getDuration(String propertyName, DoubleOrString&);
     double playbackRate();
     String direction();
     String easing();