[cq] Make chromium win trybot blocking

infra/config/cq.cfg

 # See http://luci-config.appspot.com/schemas/projects/refs:cq.cfg for the
 # documentation of this file format.
 
 version: 1
 cq_name: "v8"
 cq_status_url: "https://chromium-cq-status.appspot.com"
 hide_ref_in_committed_msg: true
 commit_burst_delay: 60
 max_commit_burst: 1
 target_ref: "refs/pending/heads/master"
@@ skipping 91 matching lines @@
         name: "v8_linux_blink_rel"
         experiment_percentage: 100
       }
       builders {
         name: "v8_linux64_sanitizer_coverage_rel"
         experiment_percentage: 100
       }
     }
     buckets {
       name: "master.tryserver.chromium.win"
-      builders {
-        name: "win_chromium_compile_dbg_ng"
-        experiment_percentage: 100
-      }
+      builders { name: "win_chromium_compile_dbg_ng" }
     }
   }
 
   sign_cla {}
 }