IDL: Treat undefined as missing for optional arguments with defaults

LayoutTests/fast/js/script-tests/custom-constructors.js

 description(
 "This test checks construction of objects with custom constructors."
 );
 
 // Image tests
 shouldBeNonNull("new Image()");
 shouldBeEqualToString("new Image().tagName", "IMG");
 
 shouldBe("new Image().height", "0");
 shouldBe("new Image().width", "0");
 shouldBe("new Image(100).width", "100");
 shouldBe("new Image(100, 200).height", "200");
 shouldBe("new Image(-100).width", "-100");
 shouldBe("new Image(-100, -200).height", "-200");
 
 shouldBeEqualToString("new Image().outerHTML","<img>");
 // FIXME: shouldBeEqualToString strips quotes from the string.
 shouldBeEqualToString("new Image(100, 100).outerHTML.replace(/\"/g, \"'\")", "<img width='100' height='100'>");
 
 // Option tests
 shouldBeNonNull("new Option()");
 shouldBeEqualToString("new Option().tagName", "OPTION");
 
 shouldBeEqualToString("new Option().innerText", "");
 shouldBeEqualToString("new Option(null).innerText", "null");
-shouldBeEqualToString("new Option(undefined).innerText", "undefined");
+shouldBeEqualToString("new Option(undefined).innerText", "");
 shouldBeEqualToString("new Option('somedata').innerText", "somedata");
 
 shouldBeEqualToString("new Option().value", "");
 shouldBeEqualToString("new Option('somedata', null).value", "null");
-shouldBeEqualToString("new Option('somedata', undefined).value", "undefined");
+shouldBeEqualToString("new Option('somedata', undefined).value", "somedata");
 shouldBeEqualToString("new Option('somedata', 'somevalue').value", "somevalue");
 
 shouldBeFalse("new Option().defaultSelected");
 shouldBeFalse("new Option('somedata', 'somevalue').defaultSelected");
 shouldBeFalse("new Option('somedata', 'somevalue', false).defaultSelected");
 shouldBeTrue("new Option('somedata', 'somevalue', true).defaultSelected");
 
 shouldBeFalse("new Option().selected");
 shouldBeFalse("new Option('somedata', 'somevalue').selected");
 shouldBeFalse("new Option('somedata', 'somevalue', false).selected");
 shouldBeFalse("new Option('somedata', 'somevalue', true).selected");
 shouldBeFalse("new Option('somedata', 'somevalue', true, false).selected");
 shouldBeTrue("new Option('somedata', 'somevalue', true, true).selected");
 
 shouldBeEqualToString("new Option().outerHTML","<option></option>");
 shouldBeEqualToString("new Option('somedata', 'somevalue', false).outerHTML.replace(/\"/g,\"'\")", "<option value='somevalue'>somedata</option>");
 shouldBeEqualToString("new Option('somedata', 'somevalue', true).outerHTML.replace(/\"/g,\"'\")", "<option value='somevalue' selected=''>somedata</option>");
 
 // Audio tests
 shouldBeNonNull("new Audio()");
 shouldBeEqualToString("new Audio().tagName", "AUDIO");
 
 shouldBeEqualToString("new Audio().src", "");
 shouldBeEqualToString("new Audio().preload", "auto");
 shouldBeEqualToString("new Audio('http://127.0.0.1/someurl').src", "http://127.0.0.1/someurl");
 shouldBeEqualToString("new Audio('http://127.0.0.1/someurl').preload", "auto");