mojo_run: make the port-in-use message helpful on Mac.

mojo/devtools/common/devtoolslib/http_server.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.
 
 import atexit
 import datetime
 import email.utils
 import errno
 import hashlib
 import logging
 import math
 import os.path
 import socket
 import subprocess
+import sys
 import tempfile
 import threading
 
 import SimpleHTTPServer
 import SocketServer
 
 _ZERO = datetime.timedelta(0)
 
 
 class UTC_TZINFO(datetime.tzinfo):
@@ skipping 205 matching lines @@
 
     http_thread = threading.Thread(target=httpd.serve_forever)
     http_thread.daemon = True
     http_thread.start()
     return httpd.server_address
   except socket.error as v:
     error_code = v[0]
     print 'Failed to start http server for %s on port %d: %s.' % (
         str(mappings), host_port, os.strerror(error_code))
     if error_code == errno.EADDRINUSE:
-      print ('  Run `fuser %d/tcp` to find out which process is using the port;'
-             % host_port)
-      print ('  or `fuser -k %d/tcp` terminate it.' % host_port)
+      if sys.platform == 'darwin':
+        find_cmd = 'lsof -i :%d' % host_port
+        terminate_cmd = (
+            'lsof -i :%d | grep LISTEN | awk \'{print $2}\' | xargs kill -9'
+            % host_port)
+      else:
+        find_cmd = 'fuser %d/tcp' % host_port
+        terminate_cmd = 'fuser -k %d/tcp' % host_port
+      print ('  Run `%s` to find out which process is using the port;'
+             % find_cmd)
+      print ('  or `%s` terminate it.' % terminate_cmd)
     print '---'
     raise