IDL: make optional arguments (without default) explicit sometimes

Source/bindings/tests/idls/TestInterfaceConstructor2.idl

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@@ skipping 14 matching lines @@
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 // Test for length > 0, overloaded constructor.
 // Need separate tests for constructors with length == 0 and length > 0,
 // and for overloaded vs. non-overloaded, if length > 0.
 // length == 0, non-overloaded just omits a block and is not worth another test.
-//
-// Also includes some [Default] arguments (instead of in
-// TestInterfaceConstructor.idl), otherwise overload resolution check string is
-// extremely long and triggers a lint warning (line length).
 [
     // 2 constructors with same type length, to test overload resolution
     Constructor(DOMString stringArg),
     Constructor(Dictionary dictionaryArg),
     Constructor(
         TestInterfaceEmpty testInterfaceEmptyArg,
         long longArg,
-        [Default=Undefined] optional DOMString defaultUndefinedOptionalStringArg,
+        optional DOMString defaultUndefinedOptionalStringArg,
         optional DOMString defaultNullStringOptionalStringArg = null,
-        [Default=Undefined] optional Dictionary defaultUndefinedOptionalDictionaryArg,
+        optional Dictionary defaultUndefinedOptionalDictionaryArg,
         optional DOMString optionalStringArg),
 ] interface TestInterfaceConstructor2 {
 };