CQ: start draining CQ.

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: "chromium"
 cq_status_url: "https://chromium-cq-status.appspot.com"
 git_repo_url: "https://chromium.googlesource.com/chromium/src"
 commit_burst_delay: 60
 max_commit_burst: 2
 
+# Drain the CQ (crbug.com/570421)
+draining_start_time: "2017-04-27T21:20:30Z"
+
 gerrit {}
 rietveld {
   url: "https://codereview.chromium.org"
 }
 
 verifiers {
   reviewer_lgtm {
     committer_list: "project-chromium-committers"
     dry_run_access_list: "project-chromium-tryjob-access"
   }
@@ skipping 76 matching lines @@
       builders { name: "win_clang" }
     }
   }
 
 # NOTE: when adding new configs to the commit queue, please contact
 # chrome-eng-review per
 # https://sites.google.com/a/chromium.org/dev/developers/testing/chromium-build-infrastructure/tour-of-the-chromium-buildbot?pli=1#TOC-Adding-new-build-configurations-and-tests-to-the-main-Chromium-waterfall-Commit-Queue
 
   sign_cla {}
 }