bindings: Fix default values of NamedConstructor's arguments

HTMLOptionElement's NamedConstructor's arguments should have
default values of "" (empty string) instead of IDL null.
(It's not allowed to initialize non-nullable DOMString with
IDL null.)

Bug: 839389
Change-Id: Ifab7058697b98be497c7e794ee173165dcaf10cc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2134027Reviewed-by: Hitoshi Yoshida <peria@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755869}

third_party/blink/renderer/bindings/scripts/web_idl/validator.py

@@ -24,6 +24,7 @@ def _all_function_likes(ir_map):
                               IRMap.IR.Kind.INTERFACE, IRMap.IR.Kind.NAMESPACE)
     for ir in irs:
         accumulated.extend(ir.constructors)
+        accumulated.extend(ir.named_constructors)
         accumulated.extend(ir.operations)
     accumulated.extend(ir_map.irs_of_kinds(IRMap.IR.Kind.CALLBACK_FUNCTION))
     return accumulated

third_party/blink/renderer/core/html/forms/html_option_element.h

@@ -38,6 +38,13 @@ class CORE_EXPORT HTMLOptionElement final : public HTMLElement {
   DEFINE_WRAPPERTYPEINFO();
 
  public:
+  static HTMLOptionElement* CreateForJSConstructor(
+      Document& document,
+      const String& data,
+      ExceptionState& exception_state) {
+    return CreateForJSConstructor(document, data, AtomicString(), false, false,
+                                  exception_state);
+  }
   static HTMLOptionElement* CreateForJSConstructor(Document&,
                                                    const String& data,
                                                    const AtomicString& value,

third_party/blink/renderer/core/html/forms/html_option_element.idl

@@ -24,8 +24,8 @@
     ConstructorCallWith=Document,
     Exposed=Window,
     HTMLConstructor,
-    NamedConstructor=Option(optional DOMString data = null,
-                            optional DOMString value = null,
+    NamedConstructor=Option(optional DOMString data = "",
+                            optional DOMString value,
                             optional boolean defaultSelected = false,
                             optional boolean selected = false),
     NamedConstructor_CallWith=Document,