Add script context with context-allocated "const this"

src/scopes.h

Index: src/scopes.h
diff --git a/src/scopes.h b/src/scopes.h
index c6baba5e29d07abf52c3b3473349dd16e6a5a7bc..83703716d24e927dfe53a4527b39dde897d3e912 100644
--- a/src/scopes.h
+++ b/src/scopes.h
@@ -355,8 +355,7 @@ class Scope: public ZoneObject {
   // "this" (and no other variable) on the native context.  Script scopes then
   // will not have a "this" declaration.
   bool has_this_declaration() const {
-    return (is_function_scope() && !is_arrow_scope()) || is_module_scope() ||
-           is_script_scope();
+    return (is_function_scope() && !is_arrow_scope()) || is_module_scope();
   }
 
   // The variable corresponding to the 'new.target' value.