stale-while-revalidate experimental implementation.

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_
 
 #include <string>
 
 #include "base/time/time.h"
 #include "net/base/completion_callback.h"
 #include "net/base/net_log.h"
 #include "net/base/request_priority.h"
 #include "net/http/http_cache.h"
 #include "net/http/http_request_headers.h"
+#include "net/http/http_response_headers.h"
 #include "net/http/http_response_info.h"
 #include "net/http/http_transaction.h"
 
 namespace net {
 
 class PartialData;
 struct HttpRequestInfo;
 struct LoadTimingInfo;
 
 // This is the transaction that is returned by the HttpCache transaction
@@ skipping 72 matching lines @@
 
   const CompletionCallback& io_callback() { return io_callback_; }
 
   const BoundNetLog& net_log() const;
 
   // Bypasses the cache lock whenever there is lock contention.
   void BypassLockForTest() {
     bypass_lock_for_test_ = true;
   }
 
+  // Used by asynchronous validations to ensure that the asynchronous validation
+  // path isn't re-entered. The LOAD_VALIDATE_CACHE flag cannot be passed to
+  // Start() via the HttpRequestInfo object because it has the side effect of
+  // causing HttpNetworkTransaction to add a Cache-Control: max-age=0 header.
+  // This method must be called before Start().
+  void ValidateInternalCache();
+
   // HttpTransaction methods:
   virtual int Start(const HttpRequestInfo* request_info,
                     const CompletionCallback& callback,
                     const BoundNetLog& net_log) OVERRIDE;
   virtual int RestartIgnoringLastError(
       const CompletionCallback& callback) OVERRIDE;
   virtual int RestartWithCertificate(
       X509Certificate* client_cert,
       const CompletionCallback& callback) OVERRIDE;
   virtual int RestartWithAuth(const AuthCredentials& credentials,
@@ skipping 183 matching lines @@
   int RestartNetworkRequest();
 
   // Called to restart a network transaction with a client certificate.
   // Returns network error code.
   int RestartNetworkRequestWithCertificate(X509Certificate* client_cert);
 
   // Called to restart a network transaction with authentication credentials.
   // Returns network error code.
   int RestartNetworkRequestWithAuth(const AuthCredentials& credentials);
 
-  // Called to determine if we need to validate the cache entry before using it.
-  bool RequiresValidation();
+  // Called to determine if we need to validate the cache entry before using it,
+  // and whether the validation should be synchronous or asynchronous.
+  HttpResponseHeaders::ValidationType RequiredValidationType();
 
   // Called to make the request conditional (to ask the server if the cached
   // copy is valid).  Returns true if able to make the request conditional.
   bool ConditionalizeRequest();
 
   // Makes sure that a 206 response is expected.  Returns true on success.
   // On success, handling_206_ will be set to true if we are processing a
   // partial entry.
   bool ValidatePartialResponse();
 
   // Handles a response validation error by bypassing the cache.
   void IgnoreRangeRequest();
 
   // Removes content-length and byte range related info if needed.
   void FixHeadersForHead();
 
+  // Launches an asynchronous revalidation based on this transaction.
+  void TriggerAsyncValidation();
+
   // Changes the response code of a range request to be 416 (Requested range not
   // satisfiable).
   void FailRangeRequest();
 
   // Setups the transaction for reading from the cache entry.
   int SetupEntryForRead();
 
   // Reads data from the network.
   int ReadFromNetwork(IOBuffer* data, int data_len);
 
@@ skipping 121 matching lines @@
 
   BeforeNetworkStartCallback before_network_start_callback_;
   BeforeProxyHeadersSentCallback before_proxy_headers_sent_callback_;
 
   DISALLOW_COPY_AND_ASSIGN(Transaction);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_CACHE_TRANSACTION_H_