Make bucket names explicit in cq.cfg.

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"
 
 rietveld {
   url: "https://codereview.chromium.org"
 }
 
 verifiers {
   reviewer_lgtm {
     committer_list: "project-v8-committers"
     dry_run_access_list: "project-v8-tryjob-access"
   }
 
   tree_status {
     tree_status_url: "https://v8-status.appspot.com"
   }
 
   try_job {
     buckets {
-      name: "tryserver.v8"
+      name: "master.tryserver.v8"
       builders { name: "v8_android_arm_compile_rel" }
       builders { name: "v8_linux64_asan_rel_ng" }
       builders {
         name: "v8_linux64_asan_rel_ng_triggered"
         triggered_by: "v8_linux64_asan_rel_ng"
       }
       builders { name: "v8_linux64_avx2_rel_ng" }
       builders {
         name: "v8_linux64_avx2_rel_ng_triggered"
         triggered_by: "v8_linux64_avx2_rel_ng"
@@ skipping 61 matching lines @@
       builders {
         name: "v8_linux64_sanitizer_coverage_rel"
         experiment_percentage: 100
       }
     }
   }
 
   sign_cla {}
 }