Revert of Remove unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/mac.py

 # Copyright (C) 2010 Google Inc. 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
@@ skipping 11 matching lines @@
 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 # DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 # THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 """Chromium Mac implementation of the Port interface."""
 
 import logging
+import signal
 
 from webkitpy.layout_tests.port import base
 
 
 _log = logging.getLogger(__name__)
 
 
 class MacPort(base.Port):
     SUPPORTED_VERSIONS = ('mac10.9', 'mac10.10', 'mac10.11', 'retina')
     port_name = 'mac'
@@ skipping 62 matching lines @@
 
     def _path_to_driver(self, target=None):
         return self._build_path_with_target(target, self.driver_name() + '.app', 'Contents', 'MacOS', self.driver_name())
 
     def _path_to_helper(self):
         binary_name = 'layout_test_helper'
         return self._build_path(binary_name)
 
     def _path_to_wdiff(self):
         return 'wdiff'