Teach URLRequest about initiator checks for First-Party-Only cookies.

net/cookies/canonical_cookie.cc

Index: net/cookies/canonical_cookie.cc
diff --git a/net/cookies/canonical_cookie.cc b/net/cookies/canonical_cookie.cc
index 2eead173bacb9065b532e2bf8831db5d00f151f4..15287e0b8b554a4e362248738c6a35866c5202b1 100644
--- a/net/cookies/canonical_cookie.cc
+++ b/net/cookies/canonical_cookie.cc
@@ -416,15 +416,9 @@ bool CanonicalCookie::IncludeForRequestURL(const GURL& url,
   // match the cookie-path.
   if (!IsOnPath(url.path()))
     return false;
-
-  // Include first-party-only cookies if:
-  //
-  // * |options| tells us to include all of them
-  // * a first-party origin is set, and they matches the origin of |url|
-  if (IsFirstPartyOnly() && !options.include_first_party_only() &&
-      !options.first_party().IsSameOriginWith(url::Origin(url))) {
+  // Don't include first-party-only cookies for non-first-party requests.
+  if (IsFirstPartyOnly() && !options.include_first_party_only_cookies())
     return false;
-  }
 
   return true;
 }