Clean up dependencies for disk_cache histogram_macros.h.

net/disk_cache/histogram_macros.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.
 
 // This file contains macros to simplify histogram reporting from the disk
 // cache. The main issue is that we want to have separate histograms for each
 // type of cache (regular vs. media, etc), without adding the complexity of
 // keeping track of a potentially large number of histogram objects that have to
 // survive the backend object that created them.
 
@@ skipping 66 matching lines @@
                                  (base::Time::Now() - initial_time).InHours())
 
 // HISTOGRAM_AGE_MS will collect time elapsed since |initial_time|, with the
 // normal resolution of the UMA_HISTOGRAM_TIMES.
 #define CACHE_HISTOGRAM_AGE_MS(name, initial_time)\
     CACHE_HISTOGRAM_TIMES(name, base::TimeTicks::Now() - initial_time)
 
 #define CACHE_HISTOGRAM_CACHE_ERROR(name, sample) \
     CACHE_HISTOGRAM_ENUMERATION(name, sample, 50)
 
-#ifdef NET_DISK_CACHE_BACKEND_IMPL_CC_
-#define BACKEND_OBJ this
-#else
-#define BACKEND_OBJ backend_
-#endif
+#define BACKEND_OBJ CACHE_HISTOGRAM_MACROS_BACKEND_IMPL_OBJ

[rvargas (doing something else), 2014/02/11 02:17:15]

Why not go all the way and let the caller define BACKEND_OBJ (aka, remove this
line)? The fact that the caller is including this file means that BACKEND_OBJ
gets defined anyway for that compilation unit.

The only weird case could be the user from chrome/net, but this file was never
intended to be used outside of disk_cache to start with, and it is rather
unfortunate that it was.

[gavinp, 2014/02/11 16:12:45]

Done. Went with BLOCKFILE_BACKEND_IMPL_OBJ, since this is blockfile cache
specific.

[rvargas (doing something else), 2014/02/11 19:41:48]

Lots of redundancy on that name IMO (BLOCKFILE is implied given that this will
live under a folder with that name (and not being a public api), and there is no
way to have an object of something that is not the implementation of a backend).
But the difference is small enough to not matter much.

 
 // Generates a UMA histogram of the given type, generating the proper name for
 // it (asking backend_->HistogramName), and adding the provided sample.
 // For example, to generate a regualar UMA_HISTOGRAM_COUNTS, this macro would
 // be used as:
 //  CACHE_UMA(COUNTS, "MyName", 0, 20);
 //  CACHE_UMA(COUNTS, "MyExperiment", 530, 55);
 // which roughly translates to:
 //  UMA_HISTOGRAM_COUNTS("DiskCache.2.MyName", 20);  // "2" is the CacheType.
 //  UMA_HISTOGRAM_COUNTS("DiskCache.2.MyExperiment_530", 55);
@@ skipping 16 matching lines @@
       case net::PNACL_CACHE:\
         CACHE_HISTOGRAM_##type(my_name.data(), sample);\
         break;\
       default:\
         NOTREACHED();\
         break;\
     }\
   }
 
 #endif  // NET_DISK_CACHE_HISTOGRAM_MACROS_H_