Cache failover to LOAD_PREFERRING_CACHE if network response suggests offline.

net/http/http_response_info.h

Index: net/http/http_response_info.h
diff --git a/net/http/http_response_info.h b/net/http/http_response_info.h
index f5f1c2425d9250007a7237689110e6bace033d5c..661cd142c05dd25dc28e017fe2ed763ed676162e 100644
--- a/net/http/http_response_info.h
+++ b/net/http/http_response_info.h
@@ -59,6 +59,11 @@ class NET_EXPORT HttpResponseInfo {
   // 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),