IDL: Use Nullable for union type return value

Source/bindings/scripts/v8_methods.py

Index: Source/bindings/scripts/v8_methods.py
diff --git a/Source/bindings/scripts/v8_methods.py b/Source/bindings/scripts/v8_methods.py
index 9c1f7c3f6db106426a22089c65db923fc68f063d..2e314626fa9e4ada22421acfb57acaf255ac261f 100644
--- a/Source/bindings/scripts/v8_methods.py
+++ b/Source/bindings/scripts/v8_methods.py
@@ -344,6 +344,8 @@ def v8_set_return_value(interface_name, method, cpp_value, for_main_world=False)
         if idl_type.is_explicit_nullable:
             # result is of type Nullable<T>
             cpp_value = 'result.get()'
+        elif idl_type.is_union_type:
+            cpp_value = 'result{index}.get()'
         else:
             cpp_value = 'result'
         release = idl_type.release
@@ -401,10 +403,9 @@ def property_attributes(method):
 
 
 def union_arguments(idl_type):
-    """Return list of ['result0Enabled', 'result0', 'result1Enabled', ...] for union types, for use in setting return value"""
-    return [arg
-            for i in range(len(idl_type.member_types))
-            for arg in ['result%sEnabled' % i, 'result%s' % i]]
+    """Return list of ['result0', 'result1', ...] for union types, for use in setting return value"""
+    return ['result%d' % i
+            for i in range(len(idl_type.member_types))]
 
 
 def argument_default_cpp_value(argument):