Introduce NewScriptScope that creates a top-level scope

src/parsing/preparser.cc

Index: src/parsing/preparser.cc
diff --git a/src/parsing/preparser.cc b/src/parsing/preparser.cc
index 8c208b42f1e26dd75779e051b40bcfe14e81d180..72c8fd4d77605c7dc517b568881faf243a356753 100644
--- a/src/parsing/preparser.cc
+++ b/src/parsing/preparser.cc
@@ -131,7 +131,7 @@ PreParser::PreParseResult PreParser::PreParseLazyFunction(
   use_counts_ = use_counts;
   // Lazy functions always have trivial outer scopes (no with/catch scopes).
   DCHECK_NULL(scope_state_);
-  Scope* top_scope = NewScope(nullptr, SCRIPT_SCOPE);
+  Scope* top_scope = NewScriptScope();
   PreParserFactory top_factory(nullptr);
   FunctionState top_state(&function_state_, &scope_state_, top_scope,
                           kNormalFunction, &top_factory);