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

net/http/http_cache_transaction.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/http/http_cache_transaction.h"
 
 #include "build/build_config.h"
 
 #if defined(OS_POSIX)
 #include <unistd.h>
@@ skipping 526 matching lines @@
     network_trans_->SetPriority(priority_);
 }
 
 void HttpCache::Transaction::SetWebSocketHandshakeStreamCreateHelper(
     WebSocketHandshakeStreamBase::CreateHelper* create_helper) {
   websocket_handshake_stream_base_create_helper_ = create_helper;
   if (network_trans_)
     network_trans_->SetWebSocketHandshakeStreamCreateHelper(create_helper);
 }
 
+void HttpCache::Transaction::SetBeforeNetworkStartCallback(
+    const BeforeNetworkStartCallback& callback) {
+  DCHECK(!network_trans_);
+  before_network_start_callback_ = callback;
+}
+
+int HttpCache::Transaction::ResumeNetworkStart() {
+  if (network_trans_)
+    return network_trans_->ResumeNetworkStart();
+  return ERR_UNEXPECTED;
+}
+
 //-----------------------------------------------------------------------------
 
 void HttpCache::Transaction::DoCallback(int rv) {
   DCHECK(rv != ERR_IO_PENDING);
   DCHECK(!callback_.is_null());
 
   read_buf_ = NULL;  // Release the buffer before invoking the callback.
 
   // Since Run may result in Read being called, clear callback_ up front.
   CompletionCallback c = callback_;
@@ skipping 301 matching lines @@
   DCHECK(mode_ & WRITE || mode_ == NONE);
   DCHECK(!network_trans_.get());
 
   send_request_since_ = TimeTicks::Now();
 
   // Create a network transaction.
   int rv = cache_->network_layer_->CreateTransaction(priority_,
                                                      &network_trans_);
   if (rv != OK)
     return rv;
+  network_trans_->SetBeforeNetworkStartCallback(before_network_start_callback_);
 
   // Old load timing information, if any, is now obsolete.
   old_network_trans_load_timing_.reset();
 
   if (websocket_handshake_stream_base_create_helper_)
     network_trans_->SetWebSocketHandshakeStreamCreateHelper(
         websocket_handshake_stream_base_create_helper_);
 
   next_state_ = STATE_SEND_REQUEST_COMPLETE;
   rv = network_trans_->Start(request_, io_callback_, net_log_);
@@ skipping 1623 matching lines @@
     default:
       NOTREACHED();
   }
 }
 
 void HttpCache::Transaction::OnIOComplete(int result) {
   DoLoop(result);
 }
 
 }  // namespace net