More polish in prep for CrOS support

tools/gpu/gpu_tools/file_server.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.
-import os
-import subprocess
-
-class FileServer(object):
-  def __init__(self, path, port=8000):
-    self._server = None
-    self._devnull = None
-    self._path = path
-    self._port = port
-
-    assert os.path.exists(path)
-    assert os.path.isdir(path)
-
-  def __enter__(self):
-    self._devnull = open(os.devnull, 'w')
-    self._server = subprocess.Popen(
-        ['python', '-m', 'SimpleHTTPServer', str(self._port)],
-        cwd=self._path,
-        stdout=self._devnull, stderr=self._devnull)
-    return self
-
-  @property
-  def url(self):
-    return 'http://localhost:%d' % self._port
-
-  def __exit__(self, *args):
-    if self._server:
-      self._server.kill()
-      self._server = None
-    if self._devnull:
-      self._devnull.close()
-      self._devnull = None
-
-  def __del__(self):
-    if self._server:
-      self._server.kill()
-    if self._devnull:
-      self._devnull.close()
-      self._devnull = None