Reland "FetchManager should not set "referer" HTTP header"

This is a reland of bd27fde7

Original change's description:
> FetchManager should not set "referer" HTTP header
>
> Instead it should use ResourceRequest::SetReferrerString and
> ResourceRequest::SetReferrerPolicy.
>
> Bug: 863769
> Change-Id: I4de47bae9aa259ace5ffb5bbdd17d6cf423931d7
> Reviewed-on: https://chromium-review.googlesource.com/1203474
> Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
> Reviewed-by: Dominic Farolino <domfarolino@gmail.com>
> Cr-Commit-Position: refs/heads/master@{#589159}

Bug: 863769
Change-Id: Ie01801ef1ab7adec166832511539b19b707ab220
Tbr: domfarolino@gmail.com
Reviewed-on: https://chromium-review.googlesource.com/1212208Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589446}

third_party/blink/renderer/core/fetch/fetch_manager.cc

@@ -858,27 +858,9 @@ void FetchManager::Loader::PerformHTTPFetch(ExceptionState& exception_state) {
   request.SetUseStreamOnResponse(true);
   request.SetExternalRequestStateFromRequestorAddressSpace(
       execution_context_->GetSecurityContext().AddressSpace());
+  request.SetReferrerString(fetch_request_data_->ReferrerString());
+  request.SetReferrerPolicy(fetch_request_data_->GetReferrerPolicy());
 
-  // "2. Append `Referer`/empty byte sequence, if |HTTPRequest|'s |referrer|
-  // is none, and `Referer`/|HTTPRequest|'s referrer, serialized and utf-8
-  // encoded, otherwise, to HTTPRequest's header list.
-  //
-  // The following code also invokes "determine request's referrer" which is
-  // written in "Main fetch" operation.
-  const ReferrerPolicy referrer_policy =
-      fetch_request_data_->GetReferrerPolicy() == kReferrerPolicyDefault
-          ? execution_context_->GetReferrerPolicy()
-          : fetch_request_data_->GetReferrerPolicy();
-  const String referrer_string =
-      fetch_request_data_->ReferrerString() == Referrer::ClientReferrerString()
-          ? execution_context_->OutgoingReferrer()
-          : fetch_request_data_->ReferrerString();
-  // Note that generateReferrer generates |no-referrer| from |no-referrer|
-  // referrer string (i.e. String()).
-  // TODO(domfarolino): Can we use ResourceRequest's SetReferrerString() and
-  // SetReferrerPolicy() instead of calling SetHTTPReferrer()?
-  request.SetHTTPReferrer(SecurityPolicy::GenerateReferrer(
-      referrer_policy, fetch_request_data_->Url(), referrer_string));
   request.SetSkipServiceWorker(is_isolated_world_);
 
   if (fetch_request_data_->Keepalive()) {

third_party/blink/renderer/core/loader/threadable_loader.cc

@@ -81,12 +81,6 @@ AtomicString CreateAccessControlRequestHeadersHeader(
     const HTTPHeaderMap& headers) {
   Vector<String> filtered_headers = CORS::CORSUnsafeRequestHeaderNames(headers);
 
-  // FetchManager may add a "referer" header.
-  // TODO(yhirano): Remove this.
-  auto it = filtered_headers.Find("referer");
-  if (it != kNotFound)
-    filtered_headers.EraseAt(it);
-
   if (!filtered_headers.size())
     return g_null_atom;
 
@@ -170,9 +164,7 @@ ThreadableLoader::CreateAccessControlPreflightRequest(
   preflight_request->SetFetchCredentialsMode(
       network::mojom::FetchCredentialsMode::kOmit);
   preflight_request->SetSkipServiceWorker(true);
-  // TODO(domfarolino): Use ReferrerString() once https://crbug.com/850813 is
-  // closed and we stop storing the referrer string as a `Referer` header.
-  preflight_request->SetReferrerString(request.HttpReferrer());
+  preflight_request->SetReferrerString(request.ReferrerString());
   preflight_request->SetReferrerPolicy(request.GetReferrerPolicy());
 
   if (request.IsExternalRequest()) {