[test] Mark slow tests on msan.

test/cctest/cctest.status

 # Copyright 2011 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 176 matching lines @@
 ##############################################################################
 ['asan == True', {
   # Skip tests not suitable for ASAN.
   'test-assembler-x64/AssemblerX64XchglOperations': [SKIP],
 }],  # 'asan == True'
 
 ##############################################################################
 ['msan == True', {
   # ICU upstream issues.
   'test-strings/CountBreakIterator': [SKIP],
+
+  # Slow tests.
+  'test-api/Threading1': [PASS, SLOW],
+  'test-api/Threading2': [PASS, SLOW],
+  'test-api/Threading3': [PASS, SLOW],
+  'test-api/Threading4': [PASS, SLOW],
 }],  # 'msan == True'
 
 ##############################################################################
 ['no_snap == True', {
 }],  # 'no_snap == True'
 
 ##############################################################################
 # TODO(machenbach): Fix application of '*'. Nosnap windows needs a separate
 # section to not overwrite the expectations for TestThatAlwaysFails.
 ['no_snap == True and system == windows', {
@@ skipping 221 matching lines @@
 ##############################################################################
 ['arch == ppc and simulator_run == True or arch == ppc64 and simulator_run == True', {
 
   # Pass but take too long with the simulator.
   'test-api/Threading1': [PASS, SLOW],
   'test-api/Threading2': [PASS, SLOW],
   'test-api/ExternalArrays': [PASS, SLOW],
 
 }],  # 'arch == ppc64 and simulator_run == True'
 ]