Support IDL attributes limited to only known values.

Source/bindings/tests/idls/TestObject.idl

Index: Source/bindings/tests/idls/TestObject.idl
diff --git a/Source/bindings/tests/idls/TestObject.idl b/Source/bindings/tests/idls/TestObject.idl
index ead532cfeed849baae48d9cd73e78c443b331e29..6672d4a84c21bfe0b0930351f7e19652f0c444be 100644
--- a/Source/bindings/tests/idls/TestObject.idl
+++ b/Source/bindings/tests/idls/TestObject.idl
@@ -74,6 +74,9 @@ callback TestCallbackFunction = void (TestEnumType formal1, TestObject formal2);
     [Reflect=customContentBooleanAttr] attribute boolean reflectedCustomBooleanAttr;
     [Reflect=customContentURLAttr, TreatNullAs=NullString, URL] attribute DOMString reflectedCustomURLAttr;
     [Reflect] attribute SVGAnimatedString animatedReflectedAttribute;
+    [Reflect, ReflectOnly=unique] attribute DOMString limitedToOnlyOneAttribute;
+    [Reflect, ReflectOnly=Per|Paal|Espen] attribute DOMString limitedToOnlyAttribute;
+    [Reflect=Other, ReflectOnly=Value1|Value2] attribute DOMString limitedToOnlyOtherAttribute;
 
     // TypedArray attribute
     attribute Float32Array typedArrayAttr;