Upgrade Symbol implementation to match current ES6 behavior.

src/hydrogen.cc

 // Copyright 2013 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 1275 matching lines @@
            !HConstant::cast(string)->HasStringValue());
     BuildCheckHeapObject(string);
     return Add<HCheckInstanceType>(string, HCheckInstanceType::IS_STRING);
   }
   return string;
 }
 
 
 HValue* HGraphBuilder::BuildWrapReceiver(HValue* object, HValue* function) {
   if (object->type().IsJSObject()) return object;
+  // FIXME: need to always wrap Symbol values (but no HType to test against..)
   if (function->IsConstant() &&
       HConstant::cast(function)->handle(isolate())->IsJSFunction()) {
     Handle<JSFunction> f = Handle<JSFunction>::cast(
         HConstant::cast(function)->handle(isolate()));
     SharedFunctionInfo* shared = f->shared();
     if (!shared->is_classic_mode() || shared->native()) return object;
   }
   return Add<HWrapReceiver>(object, function);
 }
 
@@ skipping 4325 matching lines @@
   for (int i = 1; i < types->length(); ++i) {
     PropertyAccessInfo test_info(builder_, IC::MapToType(types->at(i)), name_);
     if (!test_info.IsCompatibleForLoad(this)) return false;
   }
 
   return true;
 }
 
 
 static bool NeedsWrappingFor(Handle<HeapType> type, Handle<JSFunction> target) {
+  if (type->Is(HeapType::Symbol())) return true;
   return type->Is(HeapType::NumberOrString()) &&
       target->shared()->is_classic_mode() &&
       !target->shared()->native();
 }
 
 
 HInstruction* HOptimizedGraphBuilder::BuildLoadMonomorphic(
     PropertyAccessInfo* info,
     HValue* object,
     HValue* checked_object,
@@ skipping 5714 matching lines @@
   if (ShouldProduceTraceOutput()) {
     isolate()->GetHTracer()->TraceHydrogen(name(), graph_);
   }
 
 #ifdef DEBUG
   graph_->Verify(false);  // No full verify.
 #endif
 }
 
 } }  // namespace v8::internal