Use JSObjectVerify instead of trying to reimplement parts of it.

test/mjsunit/mjsunit.status

 # 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 979 matching lines @@
   'regress/regress-crbug-506443': [SKIP],
   'regress/regress-crbug-507070': [SKIP],
   'regress/regress-crbug-527364': [SKIP],
   'regress/regress-crbug-530598': [SKIP],
   'regress/regress-crbug-546968': [SKIP],
   'regress/regress-crbug-568477-1': [SKIP],
   'regress/regress-crbug-568477-2': [SKIP],
   'regress/regress-crbug-568477-3': [SKIP],
   'regress/regress-crbug-568477-4': [SKIP],
   'regress/regress-crbug-572590': [SKIP],
+  'regress/regress-crbug-573857': [SKIP],
   'regress/regress-deopt-gcb': [SKIP],
   'regress/regress-deopt-gc': [SKIP],
   'regress/regress-deopt-in-array-literal-spread': [SKIP],
   'regress/regress-embedded-cons-string': [SKIP],
   'regress/regress-existing-shared-function-info': [SKIP],
   'regress/regress-fast-literal-transition': [SKIP],
   'regress/regress-function-constructor-receiver': [SKIP],
   'regress/regress-handle-illegal-redeclaration': [SKIP],
   'regress/regress-inline-class-constructor': [SKIP],
   'regress/regress-inlining-function-literal-context': [SKIP],
@@ skipping 90 matching lines @@
 
 ##############################################################################
 ['gcov_coverage', {
   # Tests taking too long.
   'array-functions-prototype-misc': [SKIP],
   'strong/implicit-conversions': [SKIP],
   'strong/load-element-mutate-backing-store': [SKIP],
 }],  # 'gcov_coverage'
 
 ]