telemetry: Robustify CrOSInterface._GetSessionManagerPid().

tools/telemetry/telemetry/core/backends/chrome/cros_interface.py

Index: tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
diff --git a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
index b5add7d4e9ffef3f6f57de299a661d5c8c2fa5a2..890e0b15cefdf5d393277c81ea9b0226efea477a 100644
--- a/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
+++ b/tools/telemetry/telemetry/core/backends/chrome/cros_interface.py
@@ -297,7 +297,8 @@ class CrOSInterface(object):
     """Returns the pid of the session_manager process, given the list of
     processes."""
     for pid, process, _, _ in procs:
-      if process.startswith('/sbin/session_manager '):
+      argv = process.split()
+      if argv and os.path.basename(argv[0]) == 'session_manager':

[achuithb, 2014/06/02 08:51:20]

argv should never be empty, right?

[Daniel Erat, 2014/06/02 13:38:24]

"".split() returns an empty array. i think that a process can rewrite its argv
to be whatever it wants, so better safe than sorry, i figure.

[Daniel Erat, 2014/06/02 13:48:17]

(although i'm probably being overly paranoid, since ListProcesses() looks like
it'll fail an assert in this case. it'd probably be safer for this code to read
from /proc instead of running ps; that way it'd also be able to find the real
executable by reading the 'exe' symlink.)

         return pid
     return None