Enable gerrit-based CQ for v8

BUG=685318

Change-Id: I6654410beaca18f5d8e0791ed18d0daa46edcae0
Reviewed-on: https://chromium-review.googlesource.com/434177Reviewed-by: Aaron Gable <agable@chromium.org>
Cr-Commit-Position: refs/heads/master@{#42792}

infra/config/cq.cfg

@@ -4,9 +4,11 @@
 version: 1
 cq_name: "v8"
 cq_status_url: "https://chromium-cq-status.appspot.com"
+git_repo_url: "https://chromium.googlesource.com/v8/v8"
 commit_burst_delay: 60
 max_commit_burst: 1
 
+gerrit {}
 rietveld {
   url: "https://codereview.chromium.org"
 }