Fix MUST_USE_RESULT warning.

src/json-stringifier.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 381 matching lines @@
     return EXCEPTION;
   }
 
   int length = Smi::cast(stack_->length())->value();
   {
     DisallowHeapAllocation no_allocation;
     FixedArray* elements = FixedArray::cast(stack_->elements());
     for (int i = 0; i < length; i++) {
       if (elements->get(i) == *object) {
         AllowHeapAllocation allow_to_return_error;
-        isolate_->Throw<Object>(factory_->NewTypeError(
+        isolate_->Throw(*factory_->NewTypeError(
             "circular_structure", HandleVector<Object>(NULL, 0)));
         return EXCEPTION;
       }
     }
   }
   JSArray::EnsureSize(stack_, length + 1);
   FixedArray::cast(stack_->elements())->set(length, *object);
   stack_->set_length(Smi::FromInt(length + 1));
   return SUCCESS;
 }
@@ skipping 484 matching lines @@
       SerializeString_<false, uint8_t>(object);
     } else {
       SerializeString_<false, uc16>(object);
     }
   }
 }
 
 } }  // namespace v8::internal
 
 #endif  // V8_JSON_STRINGIFIER_H_