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

components/sync/base/data_type_histogram.cc

Index: components/sync/base/data_type_histogram.cc
diff --git a/components/sync/base/data_type_histogram.cc b/components/sync/base/data_type_histogram.cc
index b8be026a135c73a5aecefd2b73b43b50f3b9111e..45f563e0adb76712f1ffc222e645ba18d62231c0 100644
--- a/components/sync/base/data_type_histogram.cc
+++ b/components/sync/base/data_type_histogram.cc
@@ -4,10 +4,23 @@
 
 #include "components/sync/base/data_type_histogram.h"
 
+#include "base/metrics/histogram_functions.h"
 #include "base/metrics/sparse_histogram.h"
 
+const char kModelTypeMemoryHistogramPrefix[] = "Sync.ModelTypeMemoryKB.";
+
 void SyncRecordDatatypeBin(const std::string& name, int sample, int value) {
   base::HistogramBase* histogram = base::SparseHistogram::FactoryGet(
       name, base::HistogramBase::kUmaTargetedHistogramFlag);
   histogram->AddCount(sample, value);
 }
+
+void SyncRecordMemoryKbHistogram(const std::string& histogram_name_prefix,
+                                 syncer::ModelType model_type,
+                                 size_t value) {
+  std::string type_string;
+  if (RealModelTypeToNotificationType(model_type, &type_string)) {
+    std::string full_histogram_name = histogram_name_prefix + type_string;
+    base::UmaHistogramCounts1M(full_histogram_name, value / 1024);

[Ilya Sherman, 2017/06/20 20:55:43]

You can also use UmaHistogramCustomCounts if you want to preserve the bounds
that you had in the previous patch set.

+  }
+}