Allows deferral of a URLRequest just before talking to the network, at

net/url_request/url_request_http_job.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "net/url_request/url_request_http_job.h"
 
 #include "base/base_switches.h"
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
@@ skipping 396 matching lines @@
 
   if (transaction_.get()) {
     rv = transaction_->RestartWithAuth(auth_credentials_, start_callback_);
     auth_credentials_ = AuthCredentials();
   } else {
     DCHECK(request_->context()->http_transaction_factory());
 
     rv = request_->context()->http_transaction_factory()->CreateTransaction(
         priority_, &transaction_);
 
+    transaction_->SetBeforeNetworkStartCallback(base::Bind(
+        &URLRequestHttpJob::NotifyBeforeNetworkStart, base::Unretained(this)));
+
     if (rv == OK && request_info_.url.SchemeIsWSOrWSS()) {
       // TODO(ricea): Implement WebSocket throttling semantics as defined in
       // RFC6455 Section 4.1.
       base::SupportsUserData::Data* data = request_->GetUserData(
           WebSocketHandshakeStreamBase::CreateHelper::DataKey());
       if (data) {
         transaction_->SetWebSocketHandshakeStreamCreateHelper(
             static_cast<WebSocketHandshakeStreamBase::CreateHelper*>(data));
       } else {
         rv = ERR_DISALLOWED_URL_SCHEME;
@@ skipping 733 matching lines @@
     return;
 
   // The transaction started synchronously, but we need to notify the
   // URLRequest delegate via the message loop.
   base::MessageLoop::current()->PostTask(
       FROM_HERE,
       base::Bind(&URLRequestHttpJob::OnStartCompleted,
                  weak_factory_.GetWeakPtr(), rv));
 }
 
+void URLRequestHttpJob::ResumeNetworkStart() {
+  DCHECK(transaction_.get());
+  transaction_->ResumeNetworkStart();
+}
+
 bool URLRequestHttpJob::ShouldFixMismatchedContentLength(int rv) const {
   // Some servers send the body compressed, but specify the content length as
   // the uncompressed size.  Although this violates the HTTP spec we want to
   // support it (as IE and FireFox do), but *only* for an exact match.
   // See http://crbug.com/79694.
   if (rv == net::ERR_CONTENT_LENGTH_MISMATCH ||
       rv == net::ERR_INCOMPLETE_CHUNKED_ENCODING) {
     if (request_ && request_->response_headers()) {
       int64 expected_length = request_->response_headers()->GetContentLength();
       VLOG(1) << __FUNCTION__ << "() "
@@ skipping 266 matching lines @@
   return override_response_headers_.get() ?
              override_response_headers_.get() :
              transaction_->GetResponseInfo()->headers.get();
 }
 
 void URLRequestHttpJob::NotifyURLRequestDestroyed() {
   awaiting_callback_ = false;
 }
 
 }  // namespace net