Load LLVMpipe GL driver in Chromoting desktop session

This sets up LD_LIBRARY_PATH in the virtual desktop session, so that
the software-rendered GL driver (LLVMpipe) is loaded instead of any
installed hardware drivers.

BUG=366432
NOTRY=true

Review URL: https://codereview.chromium.org/317373006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275817 0039d316-1c4b-4281-b951-d872f2087c98

remoting/host/linux/linux_me2me_host.py

@@ -20,6 +20,7 @@ import logging
 import optparse
 import os
 import pipes
+import platform
 import psutil
 import platform
 import signal
@@ -254,6 +255,14 @@ class Desktop:
       if os.environ.has_key(key):
         self.child_env[key] = os.environ[key]
 
+    # Ensure that the software-rendering GL drivers are loaded by the desktop
+    # session, instead of any hardware GL drivers installed on the system.
+    self.child_env["LD_LIBRARY_PATH"] = (
+        "/usr/lib/%(arch)s-linux-gnu/mesa:"
+        "/usr/lib/%(arch)s-linux-gnu/dri:"
+        "/usr/lib/%(arch)s-linux-gnu/gallium-pipe" %
+        { "arch": platform.machine() })
+
     # Read from /etc/environment if it exists, as it is a standard place to
     # store system-wide environment settings. During a normal login, this would
     # typically be done by the pam_env PAM module, depending on the local PAM