IDL: Generate trace() method in union container types when required

Source/bindings/tests/results/core/UnionTypesCore.h

Index: Source/bindings/tests/results/core/UnionTypesCore.h
diff --git a/Source/bindings/tests/results/core/UnionTypesCore.h b/Source/bindings/tests/results/core/UnionTypesCore.h
index ed9e25225d43119aac83db1addaaeb46383a6b60..4ca08a2119da2c54dccf1f2adf89c74da53a49c2 100644
--- a/Source/bindings/tests/results/core/UnionTypesCore.h
+++ b/Source/bindings/tests/results/core/UnionTypesCore.h
@@ -80,6 +80,8 @@ public:
     PassRefPtrWillBeRawPtr<NodeList> getAsNodeList();
     void setNodeList(PassRefPtrWillBeRawPtr<NodeList>);
 
+    void trace(Visitor*);
+
 private:
     enum SpecificTypes {
         SpecificTypeNone,
@@ -158,6 +160,8 @@ public:
     String getAsString();
     void setString(String);
 
+    void trace(Visitor*);
+
 private:
     enum SpecificTypes {
         SpecificTypeNone,
@@ -275,6 +279,8 @@ public:
     TestDictionary getAsTestDictionary();
     void setTestDictionary(TestDictionary);
 
+    void trace(Visitor*);
+
 private:
     enum SpecificTypes {
         SpecificTypeNone,