Implement the "first-party-only" cookie flag.

chrome/browser/extensions/api/cookies/cookies_api.cc

Index: chrome/browser/extensions/api/cookies/cookies_api.cc
diff --git a/chrome/browser/extensions/api/cookies/cookies_api.cc b/chrome/browser/extensions/api/cookies/cookies_api.cc
index d059071dbfa1f9247c7ec32d11c135aafd0ec6bf..d3bc6e781d455b82397a06f9c5df9bbac2e888f7 100644
--- a/chrome/browser/extensions/api/cookies/cookies_api.cc
+++ b/chrome/browser/extensions/api/cookies/cookies_api.cc
@@ -399,6 +399,10 @@ void CookiesSetFunction::SetCookieOnIOThread() {
                                          : false,
       parsed_args_->details.http_only.get() ? *parsed_args_->details.http_only
                                             : false,
+      // TODO(mkwst): If we decide to ship First-party-only cookies, we'll need
+      // to extend the extension API to support them. For the moment, we'll set
+      // all cookies as non-First-party-only.
+      false,
       net::COOKIE_PRIORITY_DEFAULT,
       base::Bind(&CookiesSetFunction::PullCookie, this));
 }