web-sys: Don't remove dictionaries if required fields are removed

This commit updates the conditional binding generation for dictionaries
to ensure that a dictionary is not entirely removed if any of its
required fields are removed. If a required field is removed, however, it
cannot be constructed, so the constructor is removed.

crates/webidl/src/lib.rs

@@ -317,6 +317,7 @@ impl<'src> FirstPassRecord<'src> {
         program.dictionaries.push(ast::Dictionary {
             name: rust_ident(&camel_case_ident(def.identifier.0)),
             fields,
+            ctor: true,
         });
     }
 
@@ -784,6 +785,7 @@ impl<'src> FirstPassRecord<'src> {
         program.dictionaries.push(ast::Dictionary {
             name: rust_ident(&camel_case_ident(item.definition.identifier.0)),
             fields,
+            ctor: true,
         });
     }
 }