[HttpCache::Transaction] Ensure each state only sets the next state once

net/http/http_cache_transaction.h

 // 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.
 
 // This file declares HttpCache::Transaction, a private class of HttpCache so
 // it should only be included by http_cache.cc
 
 #ifndef NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 #define NET_HTTP_HTTP_CACHE_TRANSACTION_H_
 
@@ skipping 416 matching lines @@
   void UpdateCacheEntryStatus(
       HttpResponseInfo::CacheEntryStatus new_cache_entry_status);
 
   // Sets the response.cache_entry_status to the current cache_entry_status_.
   void SyncCacheEntryStatusToResponse();
   void RecordHistograms();
 
   // Called to signal completion of asynchronous IO.
   void OnIOComplete(int result);
 
+  // When in a DoLoop, use this to set the next state as it verifies that the
+  // state isn't set twice.
+  void TransitionToState(State state);
+
   State next_state_;
   const HttpRequestInfo* request_;
   RequestPriority priority_;
   NetLogWithSource net_log_;
   std::unique_ptr<HttpRequestInfo> custom_request_;
   HttpRequestHeaders request_headers_copy_;
   // If extra_headers specified a "if-modified-since" or "if-none-match",
   // |external_validation_| contains the value of those headers.
   ValidationHeaders external_validation_;
   base::WeakPtr<HttpCache> cache_;
@@ skipping 54 matching lines @@
   // The helper object to use to create WebSocketHandshakeStreamBase
   // objects. Only relevant when establishing a WebSocket connection.
   // This is passed to the underlying network transaction. It is stored here in
   // case the transaction does not exist yet.
   WebSocketHandshakeStreamBase::CreateHelper*
       websocket_handshake_stream_base_create_helper_;
 
   BeforeNetworkStartCallback before_network_start_callback_;
   BeforeHeadersSentCallback before_headers_sent_callback_;
 
+  // True if the Transaction is currently processing the DoLoop.
+  bool in_do_loop_;
+
   base::WeakPtrFactory<Transaction> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(Transaction);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_TRANSACTION_H_