bug 1298553 - enable chain of trust generation in the decision task. r=dustin

MozReview-Commit-ID: 7lmGt8weVgd

--HG--
extra : rebase_source : 231ff3fa94ef245399cd251b4684d2c8b1379642

.taskcluster.yml

@@ -82,6 +82,7 @@ tasks:
 
         features:
           taskclusterProxy: true
+          chainOfTrust: true
 
         # Note: This task is built server side without the context or tooling that
         # exist in tree so we must hard code the version