[runtime] Replace %to_string_fun with %_ToString.

src/macros.py

Index: src/macros.py
diff --git a/src/macros.py b/src/macros.py
index aa994fcde0cbf6c7f433ba79ca7ea7978967fbf6..f3b646b3d94e5f11c6d02d287ff996fe36bf1994 100644
--- a/src/macros.py
+++ b/src/macros.py
@@ -147,7 +147,7 @@ macro TO_INTEGER_MAP_MINUS_ZERO(arg) = (%_IsSmi(%IS_VAR(arg)) ? arg : %NumberToI
 macro TO_INT32(arg) = (arg | 0);
 macro TO_UINT32(arg) = (arg >>> 0);
 macro TO_LENGTH_OR_UINT32(arg) = (harmony_tolength ? $toLength(arg) : TO_UINT32(arg));
-macro TO_STRING_INLINE(arg) = (IS_STRING(%IS_VAR(arg)) ? arg : $nonStringToString(arg));
+macro TO_STRING(arg) = (%_ToString(arg));
 macro TO_NUMBER_INLINE(arg) = (IS_NUMBER(%IS_VAR(arg)) ? arg : $nonNumberToNumber(arg));
 macro TO_OBJECT(arg) = (%_ToObject(arg));
 macro TO_PRIMITIVE(arg) = (%_ToPrimitive(arg));