Teach CQ to watch for PDFium CLs on Gerrit

BUG=chromium:665583

Change-Id: Ief6e67dfdc71f0d16039118129109fe3541593a2
Reviewed-on: https://pdfium-review.googlesource.com/2012
Reviewed-by: dan sinclair <dsinclair@chromium.org>
diff --git a/infra/config/cq.cfg b/infra/config/cq.cfg
index 2c1d3c6..79bc4ad 100644
--- a/infra/config/cq.cfg
+++ b/infra/config/cq.cfg
@@ -6,6 +6,7 @@
 git_repo_url: "https://pdfium.googlesource.com/pdfium.git"
 cq_status_url: "https://chromium-cq-status.appspot.com"
 
+gerrit {}
 rietveld {
   url: "https://codereview.chromium.org"
 }