[CQ] Experiment: Add blink trybots to CQ.

NOTRY=true

Review URL: https://codereview.chromium.org/1496303002

Cr-Commit-Position: refs/heads/master@{#32609}

infra/config/cq.cfg

@@ -53,6 +53,13 @@ verifiers {
         triggered_by: "v8_win_rel_ng"
       }
     }
+    buckets {
+      name: "tryserver.blink"
+      builders {
+        name: "linux_blink_rel"
+        experiment_percentage: 20
+      }
+    }
   }
 
   sign_cla {}