ES6 symbols: implement name property

src/objects-debug.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 202 matching lines @@
 void HeapObject::VerifyHeapPointer(Object* p) {
   CHECK(p->IsHeapObject());
   CHECK(HEAP->Contains(HeapObject::cast(p)));
 }
 
 
 void Symbol::SymbolVerify() {
   CHECK(IsSymbol());
   CHECK(HasHashCode());
   CHECK_GT(Hash(), 0);
+  CHECK(name()->IsUndefined() || name()->IsString());
 }
 
 
 void HeapNumber::HeapNumberVerify() {
   CHECK(IsHeapNumber());
 }
 
 
 void ByteArray::ByteArrayVerify() {
   CHECK(IsByteArray());
@@ skipping 826 matching lines @@
   for (int i = 0; i < number_of_transitions(); ++i) {
     if (!CheckOneBackPointer(current_map, GetTarget(i))) return false;
   }
   return true;
 }
 
 
 #endif  // DEBUG
 
 } }  // namespace v8::internal