Add per-file OWNERS line for Cookies code in //services/network

Change-Id: Ife6e67c51e755f38dad7c1795fd2c0979943e67c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2642829Reviewed-by: Maksim Orlovich <morlovich@chromium.org>
Commit-Queue: Lily Chen <chlily@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845778}

services/network/OWNERS

@@ -39,3 +39,6 @@ per-file BUILD.gn=file://services/network/resource_scheduler/OWNERS
 # Content Security Policy
 per-file content_security_policy*=lfg@chromium.org
 per-file content_security_policy*=nasko@chromium.org
+
+# Cookies
+per-file *cookie*=file://net/cookies/OWNERS