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

net/url_request/url_request_http_job.cc

Index: net/url_request/url_request_http_job.cc
diff --git a/net/url_request/url_request_http_job.cc b/net/url_request/url_request_http_job.cc
index c0e2dd1e14027ee06e4bdfaaf332b414a0283534..e77a03b1c5347986c7e1189ae8ca12316617c3be 100644
--- a/net/url_request/url_request_http_job.cc
+++ b/net/url_request/url_request_http_job.cc
@@ -414,6 +414,9 @@ void URLRequestHttpJob::StartTransactionInternal() {
     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.
@@ -1167,6 +1170,11 @@ void URLRequestHttpJob::ContinueDespiteLastError() {
                  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