Add HttpCache histograms focussed on blocking and transaction type.

net/disk_cache/mem_backend_impl.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.
 
 // See net/disk_cache/disk_cache.h for the public interface of the cache.
 
 #ifndef NET_DISK_CACHE_MEM_BACKEND_IMPL_H__
 #define NET_DISK_CACHE_MEM_BACKEND_IMPL_H__
 
 #include "base/compiler_specific.h"
@@ skipping 44 matching lines @@
   // Insert an MemEntryImpl into the ranking list. This method is only called
   // from MemEntryImpl to insert child entries. The reference can be removed
   // by calling RemoveFromRankingList(|entry|).
   void InsertIntoRankingList(MemEntryImpl* entry);
 
   // Remove |entry| from ranking list. This method is only called from
   // MemEntryImpl to remove a child entry from the ranking list.
   void RemoveFromRankingList(MemEntryImpl* entry);
 
   // Backend interface.
+  virtual net::CacheType GetCacheType() const OVERRIDE;
   virtual int32 GetEntryCount() const OVERRIDE;
   virtual int OpenEntry(const std::string& key, Entry** entry,
                         const CompletionCallback& callback) OVERRIDE;
   virtual int CreateEntry(const std::string& key, Entry** entry,
                           const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntry(const std::string& key,
                         const CompletionCallback& callback) OVERRIDE;
   virtual int DoomAllEntries(const CompletionCallback& callback) OVERRIDE;
   virtual int DoomEntriesBetween(const base::Time initial_time,
                                  const base::Time end_time,
@@ skipping 35 matching lines @@
   int32 current_size_;
 
   net::NetLog* net_log_;
 
   DISALLOW_COPY_AND_ASSIGN(MemBackendImpl);
 };
 
 }  // namespace disk_cache
 
 #endif  // NET_DISK_CACHE_MEM_BACKEND_IMPL_H__