IDL: Union type support for attributes

LayoutTests/fast/dom/idl-union-type-unittest.html

Index: LayoutTests/fast/dom/idl-union-type-unittest.html
diff --git a/LayoutTests/fast/dom/idl-union-type-unittest.html b/LayoutTests/fast/dom/idl-union-type-unittest.html
index 0b8927fc7b93df57968d27f1c6e08417fb89d3e7..b25257981ba2df7f3eb6fafdfe8a299dcaa001f2 100644
--- a/LayoutTests/fast/dom/idl-union-type-unittest.html
+++ b/LayoutTests/fast/dom/idl-union-type-unittest.html
@@ -4,12 +4,30 @@
 description('IDL union types unittests');
 
 if (window.internals) {
+    // The conversion rule prefers string over double, hence a value which
+    // is neither double nor string will be converted using ToString().
+
     var unionTypesTest = internals.unionTypesTest();
+
+    debug('Tests for attributes');
+    shouldBeNull('unionTypesTest.doubleOrStringAttribute');
+    unionTypesTest.doubleOrStringAttribute = 3.14;
+    shouldBe('unionTypesTest.doubleOrStringAttribute', '3.14');
+    unionTypesTest.doubleOrStringAttribute = "foo";
+    shouldBeEqualToString('unionTypesTest.doubleOrStringAttribute', 'foo');
+    unionTypesTest.doubleOrStringAttribute = undefined;
+    shouldBeEqualToString('unionTypesTest.doubleOrStringAttribute', 'undefined');
+    unionTypesTest.doubleOrStringAttribute = null;
+    shouldBeEqualToString('unionTypesTest.doubleOrStringAttribute', 'null');
+    unionTypesTest.doubleOrStringAttribute = {};
+    shouldBeEqualToString('unionTypesTest.doubleOrStringAttribute', '[object Object]');
+    unionTypesTest.doubleOrStringAttribute = [];
+    shouldBeEqualToString('unionTypesTest.doubleOrStringAttribute', '');
+    debug('');
+
     debug('Tests for method arguments');
     shouldBeEqualToString('unionTypesTest.doubleOrStringArg(3.14)', 'double is passed: 3.14');
     shouldBeEqualToString('unionTypesTest.doubleOrStringArg("foo")', 'string is passed: foo');
-    // The conversion rule prefers string over double, hence a value which
-    // is neither double nor string will be converted using ToString().
     shouldBeEqualToString('unionTypesTest.doubleOrStringArg(undefined)', 'string is passed: undefined');
     shouldBeEqualToString('unionTypesTest.doubleOrStringArg(null)', 'string is passed: null');
     shouldBeEqualToString('unionTypesTest.doubleOrStringArg({})', 'string is passed: [object Object]');