Add `mojo_run --free-ports` to run servers on system-allocated ports.

mojo/devtools/common/devtoolslib/shell_config.py

 # 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.
 
 """Configuration for the shell abstraction.
 
 This module declares ShellConfig and knows how to compute it from command-line
 arguments, applying any default paths inferred from the checkout, configuration
 file, etc.
 """
@@ skipping 11 matching lines @@
 class ShellConfig(object):
   """Configuration for the shell abstraction."""
 
   def __init__(self):
     self.android = None
     self.shell_path = None
     self.origin = None
     self.map_url_list = []
     self.map_origin_list = []
     self.dev_servers = []
+    self.free_ports = False
     self.content_handlers = dict()
     self.verbose = None
 
     # Android-only.
     self.adb_path = None
     self.target_device = None
     self.logcat_tags = None
     self.require_root = False
     self.free_host_ports = False
 
@@ skipping 20 matching lines @@
                       action='store_true')
   parser.add_argument('--shell-path', help='Path of the Mojo shell binary.')
   parser.add_argument('--origin', help='Origin for mojo: URLs. This can be a '
                       'web url or a local directory path.')
   parser.add_argument('--map-url', action='append',
                       help='Define a mapping for a url in the format '
                       '<url>=<url-or-local-file-path>')
   parser.add_argument('--map-origin', action='append',
                       help='Define a mapping for a url origin in the format '
                       '<origin>=<url-or-local-file-path>')
+  parser.add_argument('--free-ports', action='store_true',
+                      help='Use system-allocated ports when spawning local '
+                      'servers. This defeats caching and thus hurts '
+                      'performance.')
   parser.add_argument('-v', '--verbose', action="store_true",
                       help="Increase output verbosity")
 
   android_group = parser.add_argument_group('Android-only',
       'These arguments apply only when --android is passed.')
   android_group.add_argument('--adb-path', help='Path of the adb binary.')
   android_group.add_argument('--target-device', help='Device to run on.')
   android_group.add_argument('--logcat-tags', help='Comma-separated list of '
                              'additional logcat tags to display.')
   android_group.add_argument('--free-host-ports', action='store_true',
                              help='Use system-allocated ports on the host when '
-                             'spawning local servers.')
+                             'spawning local servers. This still forwards to '
+                             'fixed ports on the device, so that caching '
+                             'works.')
 
   desktop_group = parser.add_argument_group('Desktop-only',
       'These arguments apply only when running on desktop.')
   desktop_group.add_argument('--use-osmesa', action='store_true',
                              help='Configure the native viewport service '
                              'for off-screen rendering.')
 
   config_file_group = parser.add_argument_group('Configuration file',
       'These arguments allow to modify the behavior regarding the mojoconfig '
       'file.')
@@ skipping 52 matching lines @@
   inferred_paths = paths.infer_paths(script_args.android, script_args.debug,
                                      script_args.target_cpu)
   shell_config = ShellConfig()
 
   shell_config.android = script_args.android
   shell_config.shell_path = (script_args.shell_path or
                              inferred_paths['shell_path'])
   shell_config.origin = script_args.origin
   shell_config.map_url_list = script_args.map_url
   shell_config.map_origin_list = script_args.map_origin
+  shell_config.free_ports = script_args.free_ports
   shell_config.verbose = script_args.verbose
 
   # Android-only.
   shell_config.adb_path = (script_args.adb_path or inferred_paths['adb_path'] or
                            'adb')
   shell_config.target_device = script_args.target_device
   shell_config.logcat_tags = script_args.logcat_tags
   shell_config.free_host_ports = script_args.free_host_ports
 
   # Desktop-only.
@@ skipping 45 matching lines @@
 
     if 'content_handlers' in config:
       try:
         for (mime_type,
              content_handler_url) in config['content_handlers'].iteritems():
           shell_config.content_handlers[mime_type] = content_handler_url
       except (ValueError, KeyError):
         raise ShellConfigurationException('Failed to parse content_handlers in '
                                           'the config file.')
   return shell_config