Disable webkit/array-iterate-backwards for debug builds.

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 26 matching lines @@
   'fast/js/deep-recursion-test': [PASS, NO_VARIANTS],
   # TODO(bmeurer,svenpanne): Investigate test failure.
   'fast/js/toString-number': [SKIP],
 }],  # ALWAYS
 ['mode == debug', {
   # Too slow in debug mode.
   'dfg-int-overflow-in-loop': [SKIP],
   'dfg-double-vote-fuzz': [SKIP],
   'reentrant-caching': [SKIP],
   'sort-large-array': [SKIP],
-  # Too slow on windows with --nocrankshaft.
-  # TODO(mstarzinger): Too slow with TF.
-  'array-iterate-backwards': [PASS, NO_VARIANTS],
+  # Too slow with --enable-slow-asserts.
+  'array-iterate-backwards': [SKIP],
 }],  # 'mode == debug'
 ['simulator', {
   # Skip tests that timeout with turbofan.
   'dfg-int-overflow-in-loop': [PASS, NO_VARIANTS],
   'array-iterate-backwards': [PASS, NO_VARIANTS],
   'function-apply-aliased': [SKIP],
 }],  # 'simulator'
 ['arch == arm64 and simulator_run == True', {
   'dfg-int-overflow-in-loop': [SKIP],
 }],  # 'arch == arm64 and simulator_run == True'
 ['dcheck_always_on == True and arch == arm64', {
   # Doesn't work with gcc 4.6 on arm64 for some reason.
   'reentrant-caching': [SKIP],
 }],  # 'dcheck_always_on == True and arch == arm64'
 
 
 ##############################################################################
 ['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 timeout.
-  'array-iterate-backwards': [SKIP]
 }],  # 'gc_stress == True and mode == debug'
 
 ##############################################################################
 ]