Remove TreatNullAs=NullString for HTMLInputElement

LayoutTests/fast/forms/submit-form-attributes.html

Index: LayoutTests/fast/forms/submit-form-attributes.html
diff --git a/LayoutTests/fast/forms/submit-form-attributes.html b/LayoutTests/fast/forms/submit-form-attributes.html
index 886ab0ca41f575c49de61558f29139f5112082c3..e30e4b264a4f1753479e84966fe7b4331aee9d69 100644
--- a/LayoutTests/fast/forms/submit-form-attributes.html
+++ b/LayoutTests/fast/forms/submit-form-attributes.html
@@ -55,18 +55,18 @@ shouldBeEqualToString('input.formTarget', 'nta');
 debug('');
 debug('Setting null for input:');
 input.formEnctype = null;
-shouldBeEqualToString('input.formEnctype', '');
-shouldBe('input.getAttribute("formEnctype")', 'null');
+shouldBeEqualToString('input.formEnctype', 'application/x-www-form-urlencoded');
+shouldBeEqualToString('input.getAttribute("formEnctype")', 'null');
 input.setAttribute('formEnctype', null);
 shouldBeEqualToString('input.formEnctype', 'application/x-www-form-urlencoded');
 input.formMethod = null;
-shouldBeEqualToString('input.formMethod', '');
-shouldBe('input.getAttribute("formMethod")', 'null');
+shouldBeEqualToString('input.formMethod', 'get');
+shouldBeEqualToString('input.getAttribute("formMethod")', 'null');
 input.setAttribute('formMethod', null);
 shouldBeEqualToString('input.formMethod', 'get');
 input.formTarget = null;
-shouldBeEqualToString('input.formTarget', '');
-shouldBe('input.getAttribute("formTarget")', 'null');
+shouldBeEqualToString('input.formTarget', 'null');
+shouldBeEqualToString('input.getAttribute("formTarget")', 'null');
 input.setAttribute('formTarget', null);
 shouldBeEqualToString('input.formTarget', 'null');