Add support for [TreatNullAs] extended attribute for reflected attributes

Source/core/html/HTMLEmbedElement.idl

Index: Source/core/html/HTMLEmbedElement.idl
diff --git a/Source/core/html/HTMLEmbedElement.idl b/Source/core/html/HTMLEmbedElement.idl
index 98dc8549e9fba6e67400f7d917ca8c10c7039721..94888dab0ae57ae9884ea9dda8cf6e01029da606 100644
--- a/Source/core/html/HTMLEmbedElement.idl
+++ b/Source/core/html/HTMLEmbedElement.idl
@@ -21,12 +21,12 @@
 [
     CustomLegacyCall,
 ] interface HTMLEmbedElement : HTMLElement {
-[Reflect] attribute DOMString align;
-[Reflect] attribute DOMString height;
-[Reflect] attribute DOMString name;
-[Reflect, URL] attribute DOMString src;
-[Reflect] attribute DOMString type;
-[Reflect] attribute DOMString width;
+[Reflect, TreatNullAs=NullString] attribute DOMString align;
+[Reflect, TreatNullAs=NullString] attribute DOMString height;
+[Reflect, TreatNullAs=NullString] attribute DOMString name;
+[Reflect, TreatNullAs=NullString, URL] attribute DOMString src;
+[Reflect, TreatNullAs=NullString] attribute DOMString type;
+[Reflect, TreatNullAs=NullString] attribute DOMString width;
 [Custom, NotEnumerable] getter boolean (unsigned long index);
 [Custom] setter boolean (unsigned long index, Node value);
 [Custom, NotEnumerable] getter Node (DOMString name);