Wait for CRD daemon process to be killed before returning.

This should mean that "/etc/init.d/chrome-remote-desktop restart" will
stop the service and won't try to start it again until the daemon is
killed.

A timeout is used to make sure that system shutdown is not paused
indefinitely if the daemon is unkillable.

Note that, since the daemon is not a child process, os.waitpid() cannot
be used for this. The psutil Python module is used instead. Some other
parts of the script have been updated as well to use psutil methods.
This is slightly safer, as psutil has some PID-reuse detection built in.

BUG=334437

Review URL: https://codereview.chromium.org/335303002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@278267 0039d316-1c4b-4281-b951-d872f2087c98

remoting/host/linux/linux_me2me_host.py

@@ -500,14 +500,15 @@ class Desktop:
     self.host_proc.stdin.close()
 
 
-def get_daemon_pid():
+def get_daemon_proc():
   """Checks if there is already an instance of this script running, and returns
-  its PID.
+  a psutil.Process instance for it.
 
   Returns:
-    The process ID of the existing daemon process, or 0 if the daemon is not
-    running.
+    A Process instance for the existing daemon process, or None if the daemon
+    is not running.
   """
+
   uid = os.getuid()
   this_pid = os.getpid()
 
@@ -535,11 +536,11 @@ def get_daemon_pid():
       if len(cmdline) < 2:
         continue
       if cmdline[0] == sys.executable and cmdline[1] == sys.argv[0]:
-        return process.pid
+        return process
     except (psutil.NoSuchProcess, psutil.AccessDenied):
       continue
 
-  return 0
+  return None
 
 
 def choose_x_session():
@@ -977,8 +978,8 @@ Web Store: https://chrome.google.com/remotedesktop"""
   # Check for a modal command-line option (start, stop, etc.)
 
   if options.get_status:
-    pid = get_daemon_pid()
-    if pid != 0:
+    proc = get_daemon_proc()
+    if proc is not None:
       print "STARTED"
     elif is_supported_platform():
       print "STOPPED"
@@ -989,23 +990,28 @@ Web Store: https://chrome.google.com/remotedesktop"""
   # TODO(sergeyu): Remove --check-running once NPAPI plugin and NM host are
   # updated to always use get-status flag instead.
   if options.check_running:
-    pid = get_daemon_pid()
-    return 0 if pid != 0 else 1
+    proc = get_daemon_proc()
+    return 1 if proc is None else 0
 
   if options.stop:
-    pid = get_daemon_pid()
-    if pid == 0:
+    proc = get_daemon_proc()
+    if proc is None:
       print "The daemon is not currently running"
     else:
-      print "Killing process %s" % pid
-      os.kill(pid, signal.SIGTERM)
+      print "Killing process %s" % proc.pid
+      proc.terminate()
+      try:
+        proc.wait(timeout=30)
+      except psutil.TimeoutExpired:
+        print "Timed out trying to kill daemon process"
+        return 1
     return 0
 
   if options.reload:
-    pid = get_daemon_pid()
-    if pid == 0:
+    proc = get_daemon_proc()
+    if proc is None:
       return 1
-    os.kill(pid, signal.SIGHUP)
+    proc.send_signal(signal.SIGHUP)
     return 0
 
   if options.add_user:
@@ -1097,8 +1103,8 @@ Web Store: https://chrome.google.com/remotedesktop"""
 
   # Determine whether a desktop is already active for the specified host
   # host configuration.
-  pid = get_daemon_pid()
-  if pid != 0:
+  proc = get_daemon_proc()
+  if proc is not None:
     # Debian policy requires that services should "start" cleanly and return 0
     # if they are already running.
     print "Service already running."