Separate xvfb.py logic into its own script

tools/isolate/isolate.py

 #!/usr/bin/env python
 # 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.
 
 """Does one of the following depending on the --mode argument:
   check     verify all the inputs exist, touches the file specified with
             --result and exits.
   hashtable puts a manifest file and hard links each of the inputs into the
             output directory.
@@ skipping 103 matching lines @@
     print >> sys.stderr, 'Using first input %s as executable' % infiles[0]
     cmd = [infiles[0]]
   outdir = None
   try:
     outdir = tempfile.mkdtemp(prefix='isolate')
     tree_creator.recreate_tree(
         outdir, indir, infiles, tree_creator.HARDLINK)
     if read_only:
       tree_creator.make_writable(outdir, True)
 
-    # TODO(maruel): Remove me. Layering violation. Used by
-    # base/base_paths_linux.cc
-    env = os.environ.copy()
-    env['CR_SOURCE_ROOT'] = outdir.encode()
     # Rebase the command to the right path.
     cmd[0] = os.path.join(outdir, cmd[0])
     logging.info('Running %s' % cmd)
-    result = subprocess.call(cmd, cwd=outdir, env=env)
+    result = subprocess.call(cmd, cwd=outdir)
     if not result and resultfile:
       # Signal the build tool that the test succeeded.
       touch(resultfile)
     return result
   finally:
     if read_only:
       tree_creator.make_writable(outdir, False)
     rmtree(outdir)
 
 
@@ skipping 64 matching lines @@
         options.mode,
         options.read_only,
         cmd)
   except tree_creator.MappingError, e:
     print >> sys.stderr, str(e)
     return 1
 
 
 if __name__ == '__main__':
   sys.exit(main())