[autotest] Bump stable to R31-4731.62.0

TEST=None
BUG=chromium:319006

Change-Id: I6bbeb48ab8202edd4eb7dc2b15682a16447a5488
Reviewed-on: https://chromium-review.googlesource.com/177139
Reviewed-by: Simran Basi <sbasi@chromium.org>
Commit-Queue: Alex Miller <milleral@chromium.org>
Tested-by: Alex Miller <milleral@chromium.org>
diff --git a/global_config.ini b/global_config.ini
index 25f83ad..6bb63ed 100644
--- a/global_config.ini
+++ b/global_config.ini
@@ -142,7 +142,7 @@
 serve_packages_from_autoserv: True
 
 [CROS]
-stable_cros_version: R30-4537.38.0
+stable_cros_version: R31-4731.62.0
 stable_build_pattern: %s-release/%s
 # The zone that all Chrome OS devices are in if they are in a lab.
 dns_zone: cros.corp.google.com