Measuring data use of different ModelTypes in Sync Service.

sync/util/data_type_histogram.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.
 
 #ifndef SYNC_UTIL_DATA_TYPE_HISTOGRAM_H_
 #define SYNC_UTIL_DATA_TYPE_HISTOGRAM_H_
 
 #include "base/metrics/histogram.h"
+#include "base/metrics/sparse_histogram.h"
 #include "base/time/time.h"
 #include "sync/internal_api/public/base/model_type.h"
 
+// This macro adds |value| to |sample| bucket of histogram |name|. |value|
+// should be greater or equal to 1 and |name| can be variable.
+#define UMA_HISTOGRAM_SPARSE_SLOWLY_WITH_VALUE(name, sample, value)     \

[Nicolas Zea, 2015/08/18 21:55:18]

I think it would be better to prefix this with SYNC rather than UMA, since it's
not something defined within the normal UMA histograms. Maybe
SYNC_RECORD_DATATYPE_BIN or something like that. Also add a comment describing
how it's used for datatypes.

[amohammadkhan, 2015/08/19 17:33:36]

Done.

+  do {                                                                  \
+    base::HistogramBase* histogram = base::SparseHistogram::FactoryGet( \
+        name, base::HistogramBase::kUmaTargetedHistogramFlag);          \
+    histogram->AddCount(sample, value);                                 \
+  } while (0)
+
 // For now, this just implements UMA_HISTOGRAM_LONG_TIMES. This can be adjusted
 // if we feel the min, max, or bucket count amount are not appropriate.
 #define SYNC_FREQ_HISTOGRAM(name, time) UMA_HISTOGRAM_CUSTOM_TIMES( \
     name, time, base::TimeDelta::FromMilliseconds(1), \
     base::TimeDelta::FromHours(1), 50)
 
 // Helper macro for datatype specific histograms. For each datatype, invokes
 // a pre-defined PER_DATA_TYPE_MACRO(type_str), where |type_str| is the string
 // version of the datatype.
 //
@@ skipping 116 matching lines @@
       case ::syncer::PROXY_TABS: \
         PER_DATA_TYPE_MACRO("Tabs"); \
         break; \
       default: \
         NOTREACHED() << "Unknown datatype " \
                      << ::syncer::ModelTypeToString(datatype);  \
     } \
   } while (0)
 
 #endif  // SYNC_UTIL_DATA_TYPE_HISTOGRAM_H_