Remove remaining unused imports in webkitpy.

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

 # Copyright (C) 2012 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.
 
 import logging
 import os
 import re
-import signal
 import sys
-import subprocess
 import threading
 import time
 
 from multiprocessing.pool import ThreadPool
 
 from webkitpy.common.system.executive import ScriptError
 from webkitpy.layout_tests.breakpad.dump_reader_multipart import DumpReaderAndroid
 from webkitpy.layout_tests.models import test_run_results
 from webkitpy.layout_tests.port import base
 from webkitpy.layout_tests.port import linux
@@ skipping 1069 matching lines @@
         return command
 
     def _read_prompt(self, deadline):
         last_char = ''
         while True:
             current_char = self._server_process.read_stdout(deadline, 1)
             if current_char == ' ':
                 if last_char in ('#', '$'):
                     return
             last_char = current_char