devtools: new workflow for multiple simultaneous `mojo_run` runs.

mojo/devtools/common/devtoolslib/shell_config.py

Index: mojo/devtools/common/devtoolslib/shell_config.py
diff --git a/mojo/devtools/common/devtoolslib/shell_config.py b/mojo/devtools/common/devtoolslib/shell_config.py
index 79a14c2ed72453ada6fb5a53e5d665976bebd289..fde356f1f6c722f6c7e17e12f948a996c09c0f79 100644
--- a/mojo/devtools/common/devtoolslib/shell_config.py
+++ b/mojo/devtools/common/devtoolslib/shell_config.py
@@ -29,7 +29,7 @@ class ShellConfig(object):
     self.map_url_list = []
     self.map_origin_list = []
     self.dev_servers = []
-    self.free_ports = False
+    self.reuse_servers = False
     self.content_handlers = dict()
     self.verbose = None
 
@@ -38,7 +38,6 @@ class ShellConfig(object):
     self.target_device = None
     self.logcat_tags = None
     self.require_root = False
-    self.free_host_ports = False
 
     # Desktop-only.
     self.use_osmesa = None
@@ -70,10 +69,10 @@ def add_shell_arguments(parser):
   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('--reuse-servers', action='store_true',
+                      help='Do not spawn any development servers. Assume that '
+                      'dev servers are already running and only forward them '
+                      'to a device if needed.')
   parser.add_argument('-v', '--verbose', action="store_true",
                       help="Increase output verbosity")
 
@@ -83,11 +82,6 @@ def add_shell_arguments(parser):
   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. 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.')
@@ -160,7 +154,7 @@ def get_shell_config(script_args):
   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.reuse_servers = script_args.reuse_servers
   shell_config.verbose = script_args.verbose
 
   # Android-only.
@@ -168,7 +162,6 @@ def get_shell_config(script_args):
                            '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.
   shell_config.use_osmesa = script_args.use_osmesa