Wrap runtime.js in a function.

src/ast-value-factory.h

Index: src/ast-value-factory.h
diff --git a/src/ast-value-factory.h b/src/ast-value-factory.h
index 3252bfde7d8a1cc5e3b235c79de6bee18f098157..454a755b79e05caf517a4c2d1fa2c95e582587c7 100644
--- a/src/ast-value-factory.h
+++ b/src/ast-value-factory.h
@@ -264,7 +264,7 @@ class AstValue : public ZoneObject {
   F(spread_iterable, "$spreadIterable")                                    \
   F(this, "this")                                                          \
   F(throw_iterator_result_not_an_object, "ThrowIteratorResultNotAnObject") \
-  F(to_string, "ToString")                                                 \
+  F(to_string, "$toString")                                                \
   F(undefined, "undefined")                                                \
   F(use_asm, "use asm")                                                    \
   F(use_strong, "use strong")                                              \