constants: Increase CANARY_TYPE build timeout.

This RELEASE BRANCH ONLY change increases the timeout for canary type
builds to be 12 hours.

BUG=chromium:558781
TEST=cbuildbot/run_tests

Change-Id: I50d00e40841ab2b0bbb3d633a35daf4071450044
Reviewed-on: https://chromium-review.googlesource.com/314885
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Don Garrett <dgarrett@chromium.org>
diff --git a/cbuildbot/constants.py b/cbuildbot/constants.py
index 0a64af3..06e1244 100644
--- a/cbuildbot/constants.py
+++ b/cbuildbot/constants.py
@@ -420,8 +420,8 @@
 # master for the lock-step master-slave builds.
 MASTER_BUILD_TIMEOUT_SECONDS = {
     PFQ_TYPE: 20 * 60,
-    # Canaries are scheduled to run every 8 hours. Leave some gap.
-    CANARY_TYPE: (7 * 60 + 50) * 60,
+    # Release builders have a 12 hour timeout.
+    CANARY_TYPE: 12 * 60 * 60,
 }
 MASTER_BUILD_TIMEOUT_DEFAULT_SECONDS = 4 * 60 * 60