Reland: [Sync] Record sync memory usage in histogram broken by datatypes

components/sync/base/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 COMPONENTS_SYNC_BASE_DATA_TYPE_HISTOGRAM_H_
 #define COMPONENTS_SYNC_BASE_DATA_TYPE_HISTOGRAM_H_
 
 #include <string>
 
 #include "base/metrics/histogram_macros.h"
 #include "base/time/time.h"
 #include "components/sync/base/model_type.h"
 
+// Prefix for histogram recording datatype's memory usage.
+extern const char kModelTypeMemoryHistogramPrefix[];
+
 // This function adds |value| to |sample| bucket of histogram |name|. |value|
 // should be greater or equal to 1 and |name| can be variable. DataTypes are
 // mapped to proper |sample| bucket by using ModelTypeToHistogramInt() function.
 // So different DataTypes play the role of different buckets in this histogram.
 void SyncRecordDatatypeBin(const std::string& name, int sample, int value);
 
+// Converts memory size |value| into kilobytes and records it into |model_type|
+// related histogram with prefix |histogram_name_prefix|.
+void SyncRecordMemoryKbHistogram(const std::string& histogram_name_prefix,
+                                 syncer::ModelType model_type,
+                                 size_t value);
+
 // 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 128 matching lines @@
       case ::syncer::EXPERIMENTS:                              \
         PER_DATA_TYPE_MACRO("Experiments");                    \
         break;                                                 \
       default:                                                 \
         NOTREACHED() << "Unknown datatype "                    \
                      << ::syncer::ModelTypeToString(datatype); \
     }                                                          \
   } while (0)
 
 #endif  // COMPONENTS_SYNC_BASE_DATA_TYPE_HISTOGRAM_H_