IDL: Support optional union type arguments with default values

Source/core/testing/UnionTypesTest.idl

Index: Source/core/testing/UnionTypesTest.idl
diff --git a/Source/core/testing/UnionTypesTest.idl b/Source/core/testing/UnionTypesTest.idl
index 282969ec181a78e8c79658e50afc11b3944c369f..efc8a1801ea0667c577082a3a8669366c03c1be1 100644
--- a/Source/core/testing/UnionTypesTest.idl
+++ b/Source/core/testing/UnionTypesTest.idl
@@ -8,4 +8,8 @@
     attribute (double or DOMString) doubleOrStringAttribute;
 
     DOMString doubleOrStringArg((double or DOMString) arg);
+
+    [ImplementedAs=doubleOrStringArg] DOMString doubleOrStringDefaultDoubleArg(optional (double or DOMString) arg = 3.14);
+    [ImplementedAs=doubleOrStringArg] DOMString doubleOrStringDefaultStringArg(optional (double or DOMString) arg = "foo");
+    [ImplementedAs=doubleOrStringArg] DOMString doubleOrStringDefaultNullArg(optional (double or DOMString)? arg = null);

[haraken, 2014/11/10 12:55:42]

Can we add:

  DOMString doubleOrStringDefaultNullArg(optional (double or DOMString)? arg =
undefined);

?

[Jens Widell, 2014/11/10 12:59:10]

Undefined is not a possible default value per spec (or in our implementation.)
The grammar only supports "null" as a special value.

 };