Put histogram code in disk_cache on a diet.

net/disk_cache/blockfile/histogram_macros_v3.h

 // Copyright 2014 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.
 
 #ifndef NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_
 #define NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_
 
 // -----------------------------------------------------------------------------
 
 // These histograms follow the definition of UMA_HISTOGRAMN_XXX except that
 // whenever the name changes (the experiment group changes), the histrogram
 // object is re-created.
-// Note: These macros are only run on one thread, so the declarations of
-// |counter| was made static (i.e., there will be no race for reinitialization).
 
 #define CACHE_HISTOGRAM_CUSTOM_COUNTS(name, sample, min, max, bucket_count) \
     do { \
-      static base::HistogramBase* counter(NULL); \
+      base::HistogramBase* counter(NULL); \
       if (!counter || name != counter->histogram_name()) \
         counter = base::Histogram::FactoryGet( \
             name, min, max, bucket_count, \
             base::Histogram::kUmaTargetedHistogramFlag); \
       counter->Add(sample); \
     } while (0)
 
 #define CACHE_HISTOGRAM_COUNTS(name, sample) CACHE_HISTOGRAM_CUSTOM_COUNTS( \
     name, sample, 1, 1000000, 50)
 
 #define CACHE_HISTOGRAM_COUNTS_10000(name, sample) \
     CACHE_HISTOGRAM_CUSTOM_COUNTS(name, sample, 1, 10000, 50)
 
 #define CACHE_HISTOGRAM_COUNTS_50000(name, sample) \
     CACHE_HISTOGRAM_CUSTOM_COUNTS(name, sample, 1, 50000000, 50)
 
 #define CACHE_HISTOGRAM_CUSTOM_TIMES(name, sample, min, max, bucket_count) \
     do { \
-      static base::HistogramBase* counter(NULL); \
+      base::HistogramBase* counter(NULL); \
       if (!counter || name != counter->histogram_name()) \
         counter = base::Histogram::FactoryTimeGet( \
             name, min, max, bucket_count, \
             base::Histogram::kUmaTargetedHistogramFlag); \
       counter->AddTime(sample); \
     } while (0)
 
 #define CACHE_HISTOGRAM_TIMES(name, sample) CACHE_HISTOGRAM_CUSTOM_TIMES( \
     name, sample, base::TimeDelta::FromMilliseconds(1), \
     base::TimeDelta::FromSeconds(10), 50)
 
 #define CACHE_HISTOGRAM_ENUMERATION(name, sample, boundary_value) do { \
-    static base::HistogramBase* counter(NULL); \
+    base::HistogramBase* counter(NULL); \
     if (!counter || name != counter->histogram_name()) \
       counter = base::LinearHistogram::FactoryGet( \
                     name, 1, boundary_value, boundary_value + 1, \
                     base::Histogram::kUmaTargetedHistogramFlag); \
     counter->Add(sample); \
   } while (0)
 
 #define CACHE_HISTOGRAM_PERCENTAGE(name, under_one_hundred) \
     CACHE_HISTOGRAM_ENUMERATION(name, under_one_hundred, 101)
 
@@ skipping 22 matching lines @@
 // For example, to generate a regualar UMA_HISTOGRAM_COUNTS, this macro would
 // be used as:
 //  CACHE_UMA(COUNTS, "MyName", 20);
 // which may translate to:
 //  UMA_HISTOGRAM_COUNTS("DiskCache3.MyName_AppCache", 20);
 //
 #define CACHE_UMA(type, name, sample) {\
     const std::string my_name =\
         CACHE_UMA_BACKEND_IMPL_OBJ->HistogramName(name);\
     switch (CACHE_UMA_BACKEND_IMPL_OBJ->cache_type()) {\
+      default:\
+        NOTREACHED();\

[rvargas (doing something else), 2014/03/17 19:41:00]

Don't add a NOTREACHED here... I'm going with no histograms by default :)

+        /* Fall-through. */\
       case net::DISK_CACHE:\
-        CACHE_HISTOGRAM_##type(my_name.data(), sample);\
-        break;\
       case net::MEDIA_CACHE:\
-        CACHE_HISTOGRAM_##type(my_name.data(), sample);\
-        break;\
       case net::APP_CACHE:\
-        CACHE_HISTOGRAM_##type(my_name.data(), sample);\
-        break;\
       case net::SHADER_CACHE:\
-        CACHE_HISTOGRAM_##type(my_name.data(), sample);\
-        break;\
       case net::PNACL_CACHE:\
         CACHE_HISTOGRAM_##type(my_name.data(), sample);\
         break;\
-      default:\
-        break;\
     }\
   }
 
 #endif  // NET_DISK_CACHE_BLOCKFILE_HISTOGRAM_MACROS_V3_H_