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

net/http/http_cache_transaction.h

Index: net/http/http_cache_transaction.h
diff --git a/net/http/http_cache_transaction.h b/net/http/http_cache_transaction.h
index 0998695962e19cf1b36f0221355487a21189af77..a8fca54228e8d8f6cadda6b947e90ab7bf24cd94 100644
--- a/net/http/http_cache_transaction.h
+++ b/net/http/http_cache_transaction.h
@@ -434,6 +434,10 @@ class HttpCache::Transaction : public HttpTransaction {
   // 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_;
@@ -508,6 +512,9 @@ class HttpCache::Transaction : public HttpTransaction {
   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);