Fix crash due to use of null transaction

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;
       }
     }
 
     if (rv == OK) {
+      transaction_->SetBeforeNetworkStartCallback(
+          base::Bind(&URLRequestHttpJob::NotifyBeforeNetworkStart,
+                     base::Unretained(this)));
+
       if (!throttling_entry_.get() ||
           !throttling_entry_->ShouldRejectRequest(*request_)) {
         rv = transaction_->Start(
             &request_info_, start_callback_, request_->net_log());
         start_time_ = base::TimeTicks::Now();
       } else {
         // Special error code for the exponential back-off module.
         rv = ERR_TEMPORARILY_THROTTLED;
       }
     }
@@ skipping 1010 matching lines @@
   return override_response_headers_.get() ?
              override_response_headers_.get() :
              transaction_->GetResponseInfo()->headers.get();
 }
 
 void URLRequestHttpJob::NotifyURLRequestDestroyed() {
   awaiting_callback_ = false;
 }
 
 }  // namespace net