[test] Mark slow test.

test/mozilla/mozilla.status

 # Copyright 2011 the V8 project authors. All rights reserved.
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 # modification, are permitted provided that the following conditions are
 # met:
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@@ skipping 150 matching lines @@
 
   # Runs out of memory while trying to build huge string of 'x'
   # characters. This takes a long time to run (~32 seconds).
   'js1_5/GC/regress-348532': [SKIP],
 
 
   # Runs for too long: huge array with getters and setters. As it says
   # in the test: "This test will probably run out of memory".
   'js1_5/extensions/regress-345967': [SKIP],
 
+  # Slow with arm64 simulator in debug.
+  'ecma_3/Statements/regress-302439': [PASS, ['mode == debug', SLOW]],
 
   ##################### FLAKY TESTS #####################
 
   # These tests time out in debug mode but pass in product mode
   'js1_5/Regress/regress-360969-05': [PASS, ['mode == debug', TIMEOUT, NO_VARIANTS]],
   'js1_5/Regress/regress-360969-06': [PASS, ['mode == debug', TIMEOUT, NO_VARIANTS]],
   'js1_5/extensions/regress-365527': [PASS, SLOW, ['mode == debug', TIMEOUT, NO_VARIANTS]],
 
   'js1_5/Regress/regress-280769-3': [PASS, ['mode == debug', FAIL]],
   'js1_5/Regress/regress-203278-1': [PASS, ['mode == debug', FAIL]],
@@ skipping 784 matching lines @@
   'ecma_3/RegExp/regress-307456': [SKIP],
   'js1_5/Regress/regress-303213': [SKIP],
   'js1_5/extensions/regress-330569': [SKIP],
   'js1_5/extensions/regress-351448': [SKIP],
   'js1_5/extensions/regress-336410-1': [SKIP],
 
   #BUG(3152): Avoid C stack overflow.
   'js1_5/extensions/regress-355497': [FAIL_OK, 'Flags: --sim-stack-size=512'],
 }],  # 'arch == arm64 and simulator_run == True'
 ]