IDL: Use Nullable for union type return value

Source/core/animation/AnimationNodeTiming.cpp

Index: Source/core/animation/AnimationNodeTiming.cpp
diff --git a/Source/core/animation/AnimationNodeTiming.cpp b/Source/core/animation/AnimationNodeTiming.cpp
index b43fba6aa1da4e14df64abd6fbfffa1f01338646..22e9fb727807fe2c5eb565b4e97886e44ca34f43 100644
--- a/Source/core/animation/AnimationNodeTiming.cpp
+++ b/Source/core/animation/AnimationNodeTiming.cpp
@@ -65,18 +65,16 @@ double AnimationNodeTiming::iterations()
 // and bindings/tests/results/V8TestInterface.cpp.
 // FIXME: It might be possible to have 'duration' defined as an attribute in the idl.
 // If possible, fix will be in a follow-up patch.
-void AnimationNodeTiming::getDuration(String propertyName, bool& element0Enabled, double& element0, bool& element1Enabled, String& element1)
+void AnimationNodeTiming::getDuration(String propertyName, Nullable<double>& element0, String& element1)
 {
     if (propertyName != "duration")
         return;
 
     if (std::isnan(m_parent->specifiedTiming().iterationDuration)) {
-        element1Enabled = true;
         element1 = "auto";
         return;
     }
-    element0Enabled = true;
-    element0 = m_parent->specifiedTiming().iterationDuration * 1000;
+    element0.set(m_parent->specifiedTiming().iterationDuration * 1000);
     return;
 }