[turbofan] Re-enable test that no longer fails.

test/mjsunit/mjsunit.status

 # Copyright 2012 the V8 project authors. All rights reserved.
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 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
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 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
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@@ skipping 84 matching lines @@
   # TODO(jarin/mstarzinger): Investigate debugger issues with TurboFan.
   'debug-evaluate-locals': [PASS, NO_VARIANTS],
   'debug-evaluate-locals-capturing': [PASS, NO_VARIANTS],
   'debug-liveedit-check-stack': [PASS, NO_VARIANTS],  # only in no-snap mode.
   'debug-liveedit-double-call': [PASS, NO_VARIANTS],
   'debug-set-variable-value': [PASS, NO_VARIANTS],
   'debug-stepout-scope-part1': [PASS, NO_VARIANTS],
   'debug-stepout-scope-part2': [PASS, NO_VARIANTS],
   'debug-stepout-scope-part3': [PASS, NO_VARIANTS],
   'es6/debug-evaluate-blockscopes': [PASS, NO_VARIANTS],
-  # Issue 4055: Scope chain length observed by debugger is off.
-  'es6/generators-debug-scopes': [PASS, NO_VARIANTS],
 
   # TODO(titzer): --always-opt incorrectly disables CrankShaft soft deopt points
   'result-table-min': [PASS, NO_VARIANTS],
   'result-table-max': [PASS, NO_VARIANTS],
   # TODO(titzer): too slow in --turbo mode due to O(n^2) graph verification.
   'regress/regress-1122': [PASS, NO_VARIANTS],
 
   # Assumptions about optimization need investigation in TurboFan.
   'regress-sync-optimized-lists': [PASS, NO_VARIANTS],
 
@@ skipping 728 matching lines @@
 ##############################################################################
 ['gcov_coverage', {
   # Tests taking too long.
   'array-functions-prototype-misc': [SKIP],
 
   # Stack overflow.
   'big-array-literal': [SKIP],
 }],  # 'gcov_coverage'
 
 ]