Enable test.dart on Mac after fixing flakiness caused by signal handlers.

tools/test_wrapper.py

 #!/usr/bin/env python
 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 import os
 import platform
 import string
 import subprocess
 import sys
 
 from utils import GuessOS
 
 def Main():
   args = sys.argv[1:]
   tools_dir = os.path.dirname(os.path.realpath(__file__))
   dart_binary_prefix = os.path.join(tools_dir, 'testing', 'bin')
   if GuessOS() == "win32":
     dart_binary = os.path.join(dart_binary_prefix, 'windows', 'dart.exe')
   else:
     dart_binary = os.path.join(dart_binary_prefix, GuessOS(), 'dart')
   current_directory = os.path.abspath('');
   client = os.path.abspath(os.path.join(tools_dir, '..'));
   if current_directory == os.path.join(client, 'runtime'):
-    if GuessOS() == "macos":
-      dart_script_name = 'test.py'
-      dart_binary = 'python'
-    else:
-      dart_script_name = 'test-runtime.dart'
+    dart_script_name = 'test-runtime.dart'
   elif current_directory == os.path.join(client, 'compiler'):
     dart_script_name = 'test-compiler.dart'
   else:
     dart_script_name = 'test.dart'
   dart_test_script = string.join([tools_dir, dart_script_name], os.sep)
   command = [dart_binary, dart_test_script] + args
   return subprocess.call(command)
 
 if __name__ == '__main__':
   sys.exit(Main())