First-Party Cookies: Wire it up as an experimental web platform feature

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index 958ef821d5d8759ddd48b7899200b93af724323f..0520c0cc1b71c6dd4c585ef4d60d1e05739114a5 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -629,11 +629,14 @@ void URLRequestHttpJob::AddCookieHeaderAndStart() {
 void URLRequestHttpJob::DoLoadCookies() {
   CookieOptions options;
   options.set_include_httponly();
-  options.set_include_first_party_only();
 
-  // TODO(mkwst): Pipe a switch down here to allow us to decide whether we
-  // should enforce "first-party only" cookies or not (by setting |options|'s
-  // first-party-url to the first-party-for-cookies value. crbug.com/459154
+  // TODO(mkwst): Drop this `if` once we decide whether or not to ship
+  // first-party cookies: https://crbug.com/459154
+  if (network_delegate() &&
+      network_delegate()->FirstPartyOnlyCookieExperimentEnabled())
+    options.set_first_party_url(request_->first_party_for_cookies());
+  else
+    options.set_include_first_party_only();
 
   GetCookieStore()->GetCookiesWithOptionsAsync(
       request_->url(), options,