Fixes the cache lock issue.

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 ab340cd4e940646f68f42abab8f35f4f4d168f8d..022479f218bc1a8008cb959f45051ac4972117ed 100644
--- a/net/http/http_response_info.h
+++ b/net/http/http_response_info.h
@@ -77,6 +77,11 @@ class NET_EXPORT HttpResponseInfo {
     // 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,
   };