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

net/http/http_transaction.h

Index: net/http/http_transaction.h
diff --git a/net/http/http_transaction.h b/net/http/http_transaction.h
index 3776998259af3f3d5223ea971922d288f5921988..39129c5a5cbe9002018a5d512a1daf93a4af9157 100644
--- a/net/http/http_transaction.h
+++ b/net/http/http_transaction.h
@@ -144,6 +144,13 @@ class NET_EXPORT_PRIVATE HttpTransaction {
   // Start(). Ownership of |create_helper| remains with the caller.
   virtual void SetWebSocketHandshakeStreamCreateHelper(
       WebSocketHandshakeStreamBase::CreateHelper* create_helper) = 0;
+
+  // Set the callback to receive notification just before network use.
+  virtual void SetBeforeNetworkStartCallback(
+      const base::Callback<void(bool*)>& callback) = 0;
+
+  // Resumes the transaction after being deferred.
+  virtual int ResumeNetworkStart() = 0;
 };
 
 }  // namespace net