Fix error message about read-only symbol properties.

R=rossberg@chromium.org
BUG=v8:3441
LOG=Y

Review URL: https://codereview.chromium.org/390783003

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@22377 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/messages.js

@@ -211,6 +211,7 @@ function NoSideEffectToString(obj) {
     }
     return str;
   }
+  if (IS_SYMBOL(obj)) return %_CallFunction(obj, SymbolToString);
   if (IS_OBJECT(obj) && %GetDataProperty(obj, "toString") === ObjectToString) {
     var constructor = %GetDataProperty(obj, "constructor");
     if (typeof constructor == "function") {