Remove unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/port/base.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 36 matching lines @@
     # Needed for Python < 2.7
     from webkitpy.thirdparty.ordered_dict import OrderedDict
 
 
 from webkitpy.common import find_files
 from webkitpy.common import read_checksum_from_png
 from webkitpy.common.memoized import memoized
 from webkitpy.common.system import path
 from webkitpy.common.system.executive import ScriptError
 from webkitpy.common.system.path import cygpath
-from webkitpy.common.system.systemhost import SystemHost
 from webkitpy.common.webkit_finder import WebKitFinder
 from webkitpy.layout_tests.layout_package.bot_test_expectations import BotTestExpectationsFactory
 from webkitpy.layout_tests.models import test_run_results
 from webkitpy.layout_tests.models.test_configuration import TestConfiguration
 from webkitpy.layout_tests.port import config as port_config
 from webkitpy.layout_tests.port import driver
 from webkitpy.layout_tests.port import server_process
 from webkitpy.layout_tests.port.factory import PortFactory
 from webkitpy.layout_tests.servers import apache_http
 from webkitpy.layout_tests.servers import pywebsocket
@@ skipping 1714 matching lines @@
 
     def __init__(self, base, args, reference_args=None):
         self.name = base
         self.base = base
         self.args = args
         self.reference_args = args if reference_args is None else reference_args
         self.tests = set()
 
     def __repr__(self):
         return "PhysicalTestSuite('%s', '%s', %s, %s)" % (self.name, self.base, self.args, self.reference_args)