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

net/url_request/url_fetcher.h

Index: net/url_request/url_fetcher.h
diff --git a/net/url_request/url_fetcher.h b/net/url_request/url_fetcher.h
index c3a1a6fa79eabd342ab711fc63a41a360ee76d32..b8642405986796923121d17927a25787a3d61a85 100644
--- a/net/url_request/url_fetcher.h
+++ b/net/url_request/url_fetcher.h
@@ -207,10 +207,12 @@ class NET_EXPORT URLFetcher {
   virtual void SetRequestContext(
       URLRequestContextGetter* request_context_getter) = 0;
 
-  // Set the URL that should be consulted for the third-party cookie
-  // blocking policy.
-  virtual void SetFirstPartyForCookies(
-      const GURL& first_party_for_cookies) = 0;
+  // Set the URL that should be considered as "initiating" the fetch. This URL
+  // will be considered the "first-party" when applying cookie blocking policy
+  // to requests, and treated as the request's initiator.
+  //
+  // TODO(mkwst): Convert this to take a 'url::Origin': https://crbug.com/577565
+  virtual void SetInitiatorURL(const GURL& initiator) = 0;
 
   // Set the key and data callback that is used when setting the user
   // data on any URLRequest objects this object creates.