Enable ES6 Symbols by default

src/d8.js

Index: src/d8.js
diff --git a/src/d8.js b/src/d8.js
index 1e64b3c50dfd38f8318bcf7f233f570665c912c4..2b927aface10e732a2bdf7e1dee8c090ec9c417f 100644
--- a/src/d8.js
+++ b/src/d8.js
@@ -1997,10 +1997,7 @@ function Stringify(x, depth) {
       } catch(e) {}
       var props = [];
       var names = Object.getOwnPropertyNames(x);
-      if (Object.getOwnPropertySymbols) {
-        // FLAG_harmony_symbols is turned on.
-        names = names.concat(Object.getOwnPropertySymbols(x));
-      }
+      names = names.concat(Object.getOwnPropertySymbols(x));
       for (var i in names) {
         var name = names[i];
         var desc = Object.getOwnPropertyDescriptor(x, name);