Reland "Implement ES6 symbol registry and predefined symbols"

src/objects-inl.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 2098 matching lines @@
   if (index >= static_cast<uint32_t>(str->length())) return false;
 
   return true;
 }
 
 
 void Object::VerifyApiCallResultType() {
 #if ENABLE_EXTRA_CHECKS
   if (!(IsSmi() ||
         IsString() ||
+        IsSymbol() ||
         IsSpecObject() ||
         IsHeapNumber() ||
         IsUndefined() ||
         IsTrue() ||
         IsFalse() ||
         IsNull())) {
     FATAL("API call returned invalid object");
   }
 #endif  // ENABLE_EXTRA_CHECKS
 }
@@ skipping 4680 matching lines @@
 #undef READ_UINT32_FIELD
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_