mojo_run: support parallel Android runs of mojo_run.

mojo/devtools/common/devtoolslib/shell.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.
 
 
 class Shell(object):
   """Represents an abstract Mojo shell."""
 
-  def serve_local_directory(self, local_dir_path, port=0):
+  def serve_local_directory(self, local_dir_path, port=0, free_host_port=False):
     """Serves the content of the local (host) directory, making it available to
     the shell under the url returned by the function.
 
     The server will run on a separate thread until the program terminates. The
     call returns immediately.
 
     Args:
       local_dir_path: path to the directory to be served
-      port: port at which the server will be available to the shell
+      port: port at which the server will be available to the shell. On Android
+          this can be different from the port on which the server runs on the
+          host.
+      free_host_port: spawn the server a system allocated port. This is ignored
+          on Linux, where |port| indicates the port on which the server will be
+          spawned.
 
     Returns:
       The url that the shell can use to access the content of |local_dir_path|.
     """
     raise NotImplementedError()
 
-  def serve_local_directories(self, mappings, port=0):
+  def serve_local_directories(self, mappings, port=0, free_host_port=False):
     """Serves the content of the local (host) directories, making it available
     to the shell under the url returned by the function.
 
     The server will run on a separate thread until the program terminates. The
     call returns immediately.
 
     Args:
       mappings: List of tuples (prefix, local_base_path_list) mapping URLs that
           start with |prefix| to one or more local directories enumerated in
           |local_base_path_list|. The prefixes should skip the leading slash.
           The first matching prefix and the first location that contains the
           requested file will be used each time.
-      port: port at which the server will be available to the shell
+      port: port at which the server will be available to the shell. On Android
+          this can be different from the port on which the server runs on the
+          host.
+      free_host_port: spawn the server a system allocated port. This is ignored
+          on Linux, where |port| indicates the port on which the server will be
+          spawned.
 
     Returns:
       The url that the shell can use to access the server.
     """
     raise NotImplementedError()
 
   def forward_host_port_to_shell(self, host_port):
     """Forwards a port on the host machine to the same port wherever the shell
     is running.
 
@@ skipping 21 matching lines @@
           terminated
 
     Returns:
       A tuple of (return_code, output, did_time_out). |return_code| is the exit
       code returned by the shell or None if the exit code cannot be retrieved.
       |output| is the stdout mingled with the stderr produced by the shell.
       |did_time_out| is True iff the shell was terminated because it exceeded
       the |timeout| and False otherwise.
     """
     raise NotImplementedError()