ES6 symbols: turn symbols into a proper primitive type

src/hydrogen.cc

Index: src/hydrogen.cc
diff --git a/src/hydrogen.cc b/src/hydrogen.cc
index 6fac3021038d6f061df07f6c1e6b3460b3d1846c..9bb8d309c25a6390c536cf4e7229e521ad5b9914 100644
--- a/src/hydrogen.cc
+++ b/src/hydrogen.cc
@@ -5089,19 +5089,7 @@ void HOptimizedGraphBuilder::VisitReturnStatement(ReturnStatement* stmt) {
       typecheck->SetSuccessorAt(1, not_spec_object);
       current_block()->Finish(typecheck);
       if_spec_object->AddLeaveInlined(return_value, state);
-      if (!FLAG_harmony_symbols) {
-        not_spec_object->AddLeaveInlined(receiver, state);
-      } else {
-        HHasInstanceTypeAndBranch* symbolcheck =
-          new(zone()) HHasInstanceTypeAndBranch(return_value, SYMBOL_TYPE);
-        HBasicBlock* is_symbol = graph()->CreateBasicBlock();
-        HBasicBlock* not_symbol = graph()->CreateBasicBlock();
-        symbolcheck->SetSuccessorAt(0, is_symbol);
-        symbolcheck->SetSuccessorAt(1, not_symbol);
-        not_spec_object->Finish(symbolcheck);
-        is_symbol->AddLeaveInlined(return_value, state);
-        not_symbol->AddLeaveInlined(receiver, state);
-      }
+      not_spec_object->AddLeaveInlined(receiver, state);
     }
   } else if (state->inlining_kind() == SETTER_CALL_RETURN) {
     // Return from an inlined setter call. The returned value is never used, the
@@ -10086,16 +10074,6 @@ void HOptimizedGraphBuilder::GenerateIsSpecObject(CallRuntime* call) {
 }
 
 
-void HOptimizedGraphBuilder::GenerateIsSymbol(CallRuntime* call) {
-  ASSERT(call->arguments()->length() == 1);
-  CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));
-  HValue* value = Pop();
-  HHasInstanceTypeAndBranch* result =
-      new(zone()) HHasInstanceTypeAndBranch(value, SYMBOL_TYPE);
-  return ast_context()->ReturnControl(result, call->id());
-}
-
-
 void HOptimizedGraphBuilder::GenerateIsFunction(CallRuntime* call) {
   ASSERT(call->arguments()->length() == 1);
   CHECK_ALIVE(VisitForValue(call->arguments()->at(0)));