follow changes in mount-passthrough processes tree

The fuse processes are now children of the minijail pid that upstart is

TEST=test_that cheets_ContainerMount

(cherry picked from commit a2e3ee06c9f3d2de533b1e5d5fed8fae034d1940)

Change-Id: I504eaa660fd9658d644f27cd3ffd30dc7b9ba114
Commit-Queue: Ereth McKnight-MacNeil <>
Tested-by: Ereth McKnight-MacNeil <>
Reviewed-by: Chris Morin <>
diff --git a/client/common_lib/cros/ b/client/common_lib/cros/
index dc9b3e3..7216861 100644
--- a/client/common_lib/cros/
+++ b/client/common_lib/cros/
@@ -333,10 +333,9 @@
 def _get_mount_passthrough_pid_internal(job_name):
     """Returns the PID of the mount-passthrough daemon job."""
     job_pid = get_job_pid(job_name)
-    # |job_pid| is the minijail process, obtain the PID of the process running
-    # inside the mount namespace.
-    # FUSE process is the only process running as chronos in the session.
-    return utils.system_output('pgrep -u chronos -s %s' % job_pid)
+    # |job_pid| is the minijail process, the fuse process should be
+    # the only direct child of the minijail process
+    return utils.system_output('pgrep -P %s' % job_pid)
 def get_mount_passthrough_pid_list():