Disable webkit/array-iterate-backwards test in --gc-stress mode for turbofan

test/webkit/webkit.status

 # Copyright 2013 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 41 matching lines @@
   'dfg-int-overflow-in-loop': [SKIP],
 }],  # 'arch == arm64 and simulator_run == True'
 
 
 ##############################################################################
 ['gc_stress == True', {
   # Tests taking too long
   'fast/js/excessive-comma-usage': [SKIP]
 }],  # 'gc_stress == True'
 
+['gc_stress == True and mode == debug', {
+  # Skip tests that timout with turbofan.
+  'array-iterate-backwards': [PASS, NO_VARIANTS]
+}],  # 'gc_stress == True and mode == debug'
+
 ##############################################################################
 ]