ES6 symbols: turn symbols into a proper primitive type

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 933a07599a455f6a19774a84b198b41e3aefdd13..c8654e65d33608698376fb53d828c92226b4727a 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1102,9 +1102,6 @@ class Object : public MaybeObject {
   // Return the object's prototype (might be Heap::null_value()).
   Object* GetPrototype(Isolate* isolate);
 
-  // Return the prototype, or the method holder for a value-like object.
-  Object* GetDelegate(Isolate* isolate);
-
   // Returns the permanent hash code associated with this object depending on
   // the actual object type.  Might return a failure in case no hash was
   // created yet or GC was caused by creation.