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

chrome/browser/predictors/resource_prefetcher.cc

Index: chrome/browser/predictors/resource_prefetcher.cc
diff --git a/chrome/browser/predictors/resource_prefetcher.cc b/chrome/browser/predictors/resource_prefetcher.cc
index 356b194b0d8bad451c11a8abb8809345bc7681c1..63c9e247979b13083485298c06aa2c81b4dfecf9 100644
--- a/chrome/browser/predictors/resource_prefetcher.cc
+++ b/chrome/browser/predictors/resource_prefetcher.cc
@@ -13,6 +13,7 @@
 #include "net/base/load_flags.h"
 #include "net/base/request_priority.h"
 #include "net/url_request/url_request_context.h"
+#include "url/origin.h"
 
 namespace {
 
@@ -134,6 +135,7 @@ void ResourcePrefetcher::SendRequest(Request* request) {
 
   url_request->set_method("GET");
   url_request->set_first_party_for_cookies(navigation_id_.main_frame_url);
+  url_request->set_initiator(url::Origin(navigation_id_.main_frame_url));
   url_request->SetReferrer(navigation_id_.main_frame_url.spec());
   url_request->SetLoadFlags(url_request->load_flags() | net::LOAD_PREFETCH);
   StartURLRequest(url_request);