Remove build_dir arg from xvfb.py

testing/scripts/run_telemetry_as_googletest.py

 #!/usr/bin/env python
 # Copyright 2015 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.
 
 """Runs isolate bundled Telemetry unittests.
 
 This script attempts to emulate the contract of gtest-style tests
 invoked via recipes. The main contract is that the caller passes the
 argument:
@@ skipping 49 matching lines @@
     del env['GTEST_SHARD_INDEX']
   sharding_args = []
   if total_shards is not None and shard_index is not None:
     sharding_args = [
       '--total-shards=%d' % total_shards,
       '--shard-index=%d' % shard_index
     ]
   cmd = [sys.executable] + rest_args + sharding_args + [
       '--write-full-results-to', args.isolated_script_test_output]
   if args.xvfb:
-    return xvfb.run_executable(cmd, '.', env)
+    return xvfb.run_executable(cmd, env)
   else:
     return common.run_command(cmd, env=env)
 
 
 # This is not really a "script test" so does not need to manually add
 # any additional compile targets.
 def main_compile_targets(args):
   json.dump([], args.output)
 
 
 if __name__ == '__main__':
   # Conform minimally to the protocol defined by ScriptTest.
   if 'compile_targets' in sys.argv:
     funcs = {
       'run': None,
       'compile_targets': main_compile_targets,
     }
     sys.exit(common.run_script(sys.argv[1:], funcs))
   sys.exit(main())