Add systemwide session file for Chromoting

This adds /etc/chrome-remote-desktop-session to the list of files that
the script looks for when deciding what session to start.

BUG=366759
NOTRY=true

Review URL: https://codereview.chromium.org/254393003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@266613 0039d316-1c4b-4281-b951-d872f2087c98

remoting/host/linux/linux_me2me_host.py

@@ -56,6 +56,7 @@ CHROME_REMOTING_GROUP_NAME = "chrome-remote-desktop"
 HOME_DIR = os.environ["HOME"]
 CONFIG_DIR = os.path.join(HOME_DIR, ".config/chrome-remote-desktop")
 SESSION_FILE_PATH = os.path.join(HOME_DIR, ".chrome-remote-desktop-session")
+SYSTEM_SESSION_FILE_PATH = "/etc/chrome-remote-desktop-session"
 
 X_LOCK_FILE_TEMPLATE = "/tmp/.X%d-lock"
 FIRST_X_DISPLAY_NUMBER = 20
@@ -80,7 +81,8 @@ g_host_hash = hashlib.md5(socket.gethostname()).hexdigest()
 def is_supported_platform():
   # Always assume that the system is supported if the config directory or
   # session file exist.
-  if os.path.isdir(CONFIG_DIR) or os.path.isfile(SESSION_FILE_PATH):
+  if (os.path.isdir(CONFIG_DIR) or os.path.isfile(SESSION_FILE_PATH) or
+      os.path.isfile(SYSTEM_SESSION_FILE_PATH)):
     return True
 
   # The host has been tested only on Ubuntu.
@@ -530,14 +532,9 @@ def choose_x_session():
     the first parameter of subprocess.Popen().  If a suitable session cannot
     be found, returns None.
   """
-  # If the session wrapper script (see below) is given a specific session as an
-  # argument (such as ubuntu-2d on Ubuntu 12.04), the wrapper will run that
-  # session instead of looking for custom .xsession files in the home directory.
-  # So it's necessary to test for these files here.
   XSESSION_FILES = [
     SESSION_FILE_PATH,
-    "~/.xsession",
-    "~/.Xsession" ]
+    SYSTEM_SESSION_FILE_PATH ]
   for startup_file in XSESSION_FILES:
     startup_file = os.path.expanduser(startup_file)
     if os.path.exists(startup_file):