Cache failover to LOAD_PREFERRING_CACHE if network response suggests offline.

net/http/http_response_info.h

 // Copyright (c) 2011 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.
 
 #ifndef NET_HTTP_HTTP_RESPONSE_INFO_H_
 #define NET_HTTP_HTTP_RESPONSE_INFO_H_
 
 #include <string>
 
 #include "base/time.h"
@@ skipping 41 matching lines @@
   bool was_fetched_via_spdy;
 
   // True if the npn was negotiated for this request.
   bool was_npn_negotiated;
 
   // True if the request was fetched via an explicit proxy.  The proxy could
   // be any type of proxy, HTTP or SOCKS.  Note, we do not know if a
   // transparent proxy may have been involved.
   bool was_fetched_via_proxy;
 
+  // True if the request was fetched from cache rather than the network
+  // because of a LOAD_PREFERRING_CACHE or LOAD_CACHE_RETURN_IF_OFFLINE

[rvargas (doing something else), 2013/03/05 02:58:19]

Why set a flag when the request is issued with LOAD_PREFERRING_CACHE?

If we do that, having a flag that says "cache_override" when we do exactly what
the user is asking for is weird.

[Randy Smith (Not in Mondays), 2013/03/05 23:16:14]

Well, that answers another question I asked you :-}.  I'll change this.  

Having said that, my thought was that if we overrode the "normal" cache
behavior, we should indicate it.  As you've pointed out, LOAD_PREFERRING_CACHE
doesn't always use the cache, so there is information returned in that case. 
But I have no use case for that information, so I'm happy to nuke it.

+  // flag.
+  bool was_cache_override;

[rvargas (doing something else), 2013/03/05 02:58:19]

nit: move after was_cached, and maybe convey instead that the system is offline.

[Randy Smith (Not in Mondays), 2013/03/05 23:16:14]

Done, though I phrased it as "was unable to contact the server" since I'm also
trying to allow for network partition or partial offline.  Let me know if you'd
like me to change the name of the flag as well.

[rvargas (doing something else), 2013/03/06 03:11:48]

yes, I think it is better to change the name too. cache_override is not really
self explanatory. The information that we are trying to convey is that the rest
of the page should be loaded assuming the machine cannot contact the server,
right?

[Randy Smith (Not in Mondays), 2013/03/06 22:55:55]

SG.  I used "server_data_unavailable"; let me know if you'd like something
different.

+
   // Remote address of the socket which fetched this resource.
   //
   // NOTE: If the response was served from the cache (was_cached is true),
   // the socket address will be set to the address that the content came from
   // originally.  This is true even if the response was re-validated using a
   // different remote address, or if some of the content came from a byte-range
   // request to a different address.
   HostPortPair socket_address;
 
   // Protocol negotiated with the server.
@@ skipping 26 matching lines @@
   // The "Vary" header data for this response.
   HttpVaryData vary_data;
 
   // Any metadata asociated with this resource's cached data.
   scoped_refptr<IOBufferWithSize> metadata;
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_RESPONSE_INFO_H_