Fix GC-unsafe use of BreakLocationIterator.

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
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@@ skipping 226 matching lines @@
   'compiler/osr-regress-max-locals': [PASS, NO_VARIANTS],
   'math-floor-of-div': [PASS, NO_VARIANTS],
   'unicodelctest': [PASS, NO_VARIANTS],
   'unicodelctest-no-optimization': [PASS, NO_VARIANTS],
 
   # Too slow for gc stress.
   'asm/embenchen/box2d': [SKIP],
 
   # Issue 3723.
   'regress/regress-3717': [SKIP],
-  # Issue 3776.
-  'debug-constructor': [SKIP],
-  'debug-stepframe': [SKIP],
-  'debug-stepout-scope-part2': [SKIP],
-  'debug-stepout-scope-part5': [SKIP],
-  'debug-stepout-scope-part6': [SKIP],
 }],  # 'gc_stress == True'
 
 ##############################################################################
 ['byteorder == big', {
   # Emscripten requires little-endian, skip all tests on big endian platforms.
   'asm/embenchen/*': [SKIP],
 }],  # 'byteorder == big'
 
 ##############################################################################
 ['arch == arm64 or arch == android_arm64', {
@@ skipping 323 matching lines @@
   'never-optimize': [SKIP],
   'regress/regress-2185-2': [SKIP],
   'harmony/object-observe': [SKIP],
   'readonly': [SKIP],
   'array-feedback': [SKIP],
 
   # Deopt every n garbage collections collides with deopt every n times.
   'regress/regress-2653': [SKIP],
 }],  # 'deopt_fuzzer == True'
 ]