Fixes the cache lock issue.

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/time.h"
@@ skipping 59 matching lines @@
     ENTRY_USED,
     // The response was validated and served from the cache. Implies was_cached
     // && network_accessed.
     ENTRY_VALIDATED,
     // There was a stale entry in the cache that was updated. Implies
     // !was_cached && network_accessed.
     ENTRY_UPDATED,
     // The HTTP request didn't allow a conditional request. Implies !was_cached
     // && network_accessed.
     ENTRY_CANT_CONDITIONALIZE,
+    // Request joins the already created SharedWriters.

[jkarlin, 2017/02/03 18:26:20]

Do we need these two new states? They don't seem congruous with the rest of the
enum. IE ENTRY_JOIN_SHARED_WRITING essentially is a subset of ENTRY_USED?

[shivanisha, 2017/02/06 21:14:11]

ENTRY_JOIN_SHARED_WRITING is different from ENTRY_USED because ENTRY_USED
signifies that the complete response was read from the cache and network was not
accessed.
Sum of HttpCache.AccessToDone.JoinSharedWriting and
HttpCache.AccessToDone.InitiateSharedWriting will give the count of shared
writing transactions out of a total of "not cached" and "updated".

ENTRY_DOOM_SHARED_WRITING is different from ENTRY_UPDATED because it means that
some transactions are still reading from the shared writing entry while these
transactions access the response from the network.

+    ENTRY_JOIN_SHARED_WRITING,
+    // Validation is not a match and SharedWriters exists, request dooms the
+    // shared writing entry and gets the response from the network.
+    ENTRY_DOOM_SHARED_WRITING,

[jkarlin, 2017/02/03 18:26:20]

If you edit this enum you need to edit the enum in histograms.xml accordingly.

[shivanisha, 2017/02/06 21:14:11]

I cannot find the definition of HttpCache.AccessToDone being associated with an
enum in histograms.xml. Am I missing something?

     ENTRY_MAX,
   };
 
   HttpResponseInfo();
   HttpResponseInfo(const HttpResponseInfo& rhs);
   ~HttpResponseInfo();
   HttpResponseInfo& operator=(const HttpResponseInfo& rhs);
   // Even though we could get away with the copy ctor and default operator=,
   // that would prevent us from doing a bunch of forward declaration.
 
@@ skipping 103 matching lines @@
 
   // Any metadata asociated with this resource's cached data.
   scoped_refptr<IOBufferWithSize> metadata;
 
   static std::string ConnectionInfoToString(ConnectionInfo connection_info);
 };
 
 }  // namespace net
 
 #endif  // NET_HTTP_HTTP_RESPONSE_INFO_H_