ES6 symbols: turn symbols into a proper primitive type

src/hydrogen-instructions.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 1259 matching lines @@
   parameter_count()->PrintNameTo(stream);
   stream->Add(" values)");
 }
 
 
 Representation HBranch::observed_input_representation(int index) {
   static const ToBooleanStub::Types tagged_types(
       ToBooleanStub::UNDEFINED |
       ToBooleanStub::NULL_TYPE |
       ToBooleanStub::SPEC_OBJECT |
-      ToBooleanStub::STRING);
+      ToBooleanStub::STRING |
+      ToBooleanStub::SYMBOL);
   if (expected_input_types_.ContainsAnyOf(tagged_types)) {
     return Representation::Tagged();
   } else if (expected_input_types_.Contains(ToBooleanStub::HEAP_NUMBER)) {
     return Representation::Double();
   } else if (expected_input_types_.Contains(ToBooleanStub::SMI)) {
     return Representation::Integer32();
   } else {
     return Representation::None();
   }
 }
@@ skipping 2227 matching lines @@
 
 
 void HCheckFunction::Verify() {
   HInstruction::Verify();
   ASSERT(HasNoUses());
 }
 
 #endif
 
 } }  // namespace v8::internal