Parser: store parameters in a ThreadedList instead of ZoneList.

src/parsing/parser-base.h

Index: src/parsing/parser-base.h
diff --git a/src/parsing/parser-base.h b/src/parsing/parser-base.h
index 3d486b88857fb003ec07c63f76701d8c97afec29..1d609db82902e0927d8bce8bfda00542a2383e19 100644
--- a/src/parsing/parser-base.h
+++ b/src/parsing/parser-base.h
@@ -3500,10 +3500,7 @@ void ParserBase<Impl>::ParseFormalParameterList(FormalParametersT* parameters,
     }
   }
 
-  for (int i = 0; i < parameters->arity; ++i) {
-    auto parameter = parameters->at(i);
-    impl()->DeclareFormalParameter(parameters->scope, parameter);
-  }
+  impl()->DeclareFormalParameters(parameters->scope, parameters->params);
 }
 
 template <typename Impl>