ES6 symbols: filter symbols form for-in loops and Object.keys

src/property-details.h

 // 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 24 matching lines @@
 // Ecma-262 3rd 8.6.1
 enum PropertyAttributes {
   NONE              = v8::None,
   READ_ONLY         = v8::ReadOnly,
   DONT_ENUM         = v8::DontEnum,
   DONT_DELETE       = v8::DontDelete,
 
   SEALED            = DONT_ENUM | DONT_DELETE,
   FROZEN            = SEALED | READ_ONLY,
 
+  SYMBOLIC          = 8,  // Used to filter symbol names
+  DONT_SHOW         = DONT_ENUM | SYMBOLIC,
   ABSENT            = 16  // Used in runtime to indicate a property is absent.
   // ABSENT can never be stored in or returned from a descriptor's attributes
   // bitfield.  It is only used as a return value meaning the attributes of
   // a non-existent property.
 };
 
 
 namespace v8 {
 namespace internal {
 
@@ skipping 83 matching lines @@
   PropertyDetails(int value, int pointer) {
       value_ = DescriptorPointer::update(value, pointer);
   }
 
   uint32_t value_;
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_PROPERTY_DETAILS_H_