Add recipe roll tryjob to depot_tools CQ as experimental.

Depends on http://crrev.com/1787173003.

BUG=594265

Review-Url: https://codereview.chromium.org/1792823002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@300365 0039d316-1c4b-4281-b951-d872f2087c98

infra/config/cq.cfg

@@ -33,6 +33,10 @@ verifiers {
       builders {
         name: "Depot Tools Presubmit"
       }
+      builders {
+        name: "Recipe Roll Downstream Tester"
+        experiment_percentage: 100
+      }
     }
   }
 }