[turbofan] Turn JSContextSpecializer into an AdvancedReducer.

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
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 360 matching lines @@
   'math-floor-of-div': [PASS, SLOW],
   'mirror-object': [PASS, SLOW],
   'packed-elements': [PASS, SLOW],
   'regress/regress-1122': [PASS, SLOW],
   'regress/regress-2185-2': [PASS, SLOW],
   'regress/regress-2185': [PASS, SLOW],
   'regress/regress-2790': [PASS, SLOW],
   'regress/regress-331444': [PASS, SLOW],
   'regress/regress-490': [PASS, SLOW],
   'regress/regress-crbug-217858': [PASS, SLOW],
+  'regress/regress-crbug-491062': [PASS, SLOW],
   'regress/regress-create-exception': [PASS, SLOW],
   'regress/regress-json-stringify-gc': [PASS, SLOW],
   'string-indexof-2': [PASS, SLOW],
   'unicodelctest-no-optimization': [PASS, SLOW],
   'unicodelctest': [PASS, SLOW],
   'unicode-test': [PASS, SLOW],
 }],  # 'arch == arm64'
 
 ['arch == arm64 and mode == debug and simulator_run == True', {
 
@@ skipping 270 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'
 ]