[Android] Lazily import lighttpd_server.

build/android/pylib/base/base_test_runner.py

 # Copyright (c) 2012 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 """Base class for running tests on a single device."""
 
 # TODO(jbudorick) Deprecate and remove this class and all subclasses after
 # any relevant parts have been ported to the new environment + test instance
 # model.
 
 import logging
 
 from devil.android import device_utils
 from devil.android import forwarder
 from devil.android import ports
 from pylib.valgrind_tools import CreateTool
 # TODO(frankf): Move this to pylib/utils
-import lighttpd_server
 
 
 # A file on device to store ports of net test server. The format of the file is
 # test-spawner-server-port:test-server-port
 NET_TEST_SERVER_PORT_INFO_FILE = 'net-test-server-ports'
 
 
 class BaseTestRunner(object):
   """Base class for running tests on a single device."""
 
@@ skipping 50 matching lines @@
 
   def LaunchTestHttpServer(self, document_root, port=None,
                            extra_config_contents=None):
     """Launches an HTTP server to serve HTTP tests.
 
     Args:
       document_root: Document root of the HTTP server.
       port: port on which we want to the http server bind.
       extra_config_contents: Extra config contents for the HTTP server.
     """
+    import lighttpd_server
     self._http_server = lighttpd_server.LighttpdServer(
         document_root, port=port, extra_config_contents=extra_config_contents)
     if self._http_server.StartupHttpServer():
       logging.info('http server started: http://localhost:%s',
                    self._http_server.port)
     else:
       logging.critical('Failed to start http server')
     self._ForwardPortsForHttpServer()
     return (self._forwarder_device_port, self._http_server.port)
 
@@ skipping 30 matching lines @@
     # will be left open even after the forwarder has been killed.
     if not ports.IsDevicePortUsed(self.device, self._forwarder_device_port):
       self._ForwardPortsForHttpServer()
 
   def ShutdownHelperToolsForTestSuite(self):
     """Shuts down the server and the forwarder."""
     if self._http_server:
       self._UnmapPorts([(self._forwarder_device_port, self._http_server.port)])
       self._http_server.ShutdownHttpServer()