Remove remaining unused imports in webkitpy.

third_party/WebKit/Tools/Scripts/webkitpy/performance_tests/perftest.py

 # Copyright (C) 2012 Google Inc. All rights reserved.
 # Copyright (C) 2012 Zoltan Horvath, Adobe Systems Incorporated. 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
@@ skipping 10 matching lines @@
 # A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 # OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 # 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.
 
 
-import errno
 import logging
 import math
 import re
-import signal
 
-from webkitpy.layout_tests.controllers.test_result_writer import TestResultWriter
 from webkitpy.layout_tests.port.driver import DriverInput
-from webkitpy.layout_tests.port.driver import DriverOutput
 
 DEFAULT_TEST_RUNNER_COUNT = 4
 
 _log = logging.getLogger(__name__)
 
 
 class PerfTestMetric(object):
 
     def __init__(self, metric, unit=None, iterations=None):
         # FIXME: Fix runner.js to report correct metric names
@@ skipping 263 matching lines @@
         (re.compile(r'^Dromaeo/'), SingleProcessPerfTest),
         (re.compile(r'^inspector/'), ChromiumStylePerfTest),
     ]
 
     @classmethod
     def create_perf_test(cls, port, test_name, path, test_runner_count=DEFAULT_TEST_RUNNER_COUNT):
         for (pattern, test_class) in cls._pattern_map:
             if pattern.match(test_name):
                 return test_class(port, test_name, path, test_runner_count)
         return PerfTest(port, test_name, path, test_runner_count)