Teach skydb about the --trace-startup flag

sky/tools/skydb

 #!/usr/bin/env python
 # Copyright 2014 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.
 
 from skypy.skyserver import SkyServer
 import argparse
 import json
 import logging
 import os
@@ skipping 95 matching lines @@
             '--content-handlers=%s' % ','.join(content_handlers),
             '--url-mappings=mojo:window_manager=mojo:kiosk_wm',
             '--args-for=mojo:sky_debugger %d' % remote_command_port,
             'mojo:sky_debugger',
         ]
 
         if args.url_or_path:
             shell_args.append(
                 '--args-for=mojo:window_manager %s' % self._url_from_args(args))
 
+        if args.trace_startup:
+            shell_args.append('--trace-startup')
+
         # Map all mojo: urls to http: urls using the --origin command.
         build_dir_url = SkyServer.url_for_path(
             remote_server_port,
             self.pids['sky_server_root'],
             self.pids['build_dir'])
 
         # TODO(eseidel): We should do this on linux, but we need to fix
         # mojo http loading to be faster first.
         if is_android:
             shell_args += ['--origin=%s' % build_dir_url]
@@ skipping 433 matching lines @@
         start_parser.add_argument('--gdb', action='store_true')
         start_parser.add_argument('--command-port', type=int,
             default=DEFAULT_SKY_COMMAND_PORT)
         start_parser.add_argument('--use-osmesa', action='store_true',
             default=self._in_chromoting())
         start_parser.add_argument('build_dir', type=str)
         start_parser.add_argument('url_or_path', nargs='?', type=str,
             default=DEFAULT_URL)
         start_parser.add_argument('--show-command', action='store_true',
             help='Display the shell command and exit')
+        start_parser.add_argument('--trace-startup', action='store_true')
         start_parser.set_defaults(func=self.start_command)
 
         stop_parser = subparsers.add_parser('stop',
             help=('stop sky (as listed in %s)' % PID_FILE_PATH))
         stop_parser.set_defaults(func=self.stop_command)
 
         pids_parser = subparsers.add_parser('pids',
             help='dump the current skydb pids file')
         pids_parser.set_defaults(func=self.pids_command)
 
@@ skipping 31 matching lines @@
         load_parser.set_defaults(func=self.load_command)
 
         args = parser.parse_args()
         args.func(args)
 
         self._write_pid_file(PID_FILE_PATH, self.pids)
 
 
 if __name__ == '__main__':
     SkyDebugger().main()