Re-enable regress-crbug-501711 and regress-4279 for --isolates tests

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
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@@ skipping 235 matching lines @@
   'asm/poppler/*': [PASS, SLOW, FAST_VARIANTS],
   'asm/sqlite3/*': [PASS, SLOW, FAST_VARIANTS],
 
   # BUG(v8:3838).
   'regress/regress-3116': [PASS, ['isolates', FLAKY]],
 
   # BUG(chromium:508074). Remove this once the issue is fixed.
   'harmony/arrow-rest-params': [PASS, NO_VARIANTS],
   'harmony/rest-params': [PASS, ['no_snap == True', NO_VARIANTS]],
 
-  # BUG(v8:4378).
-  'regress/regress-crbug-501711': [PASS, ['isolates', SKIP]],
-  'regress/regress-4279': [PASS, ['isolates', SKIP]],
-
   # BUG(chromium:518748)
   'regress/regress-crbug-518748': [PASS, ['mode == debug or arch == arm', SKIP]],
 }],  # ALWAYS
 
 ['novfp3 == True', {
   'asm/embenchen/box2d': [SKIP],
   'asm/embenchen/zlib': [SKIP],
   'asm/embenchen/memops': [SKIP],
   'asm/embenchen/lua_binarytrees': [SKIP],
 }],  # novfp3 == True
@@ skipping 406 matching lines @@
   'regress/regress-2653': [SKIP],
 }],  # 'deopt_fuzzer == True'
 
 ##############################################################################
 ['arch == ppc and simulator_run == True or arch == ppc64 and simulator_run == True', {
 
   # take too long with the simulator.
   'regress/regress-1132': [SKIP],
 }],  # 'arch == ppc and simulator_run == True'
 ]