Add support for persistent sparse histograms.

base/metrics/sample_map.cc

Index: base/metrics/sample_map.cc
diff --git a/base/metrics/sample_map.cc b/base/metrics/sample_map.cc
index e276b91643b6a4fa567b2e4f84eb09b94a92a38c..4253d54f8103c2dfca598bb003681c1f522a3a52 100644
--- a/base/metrics/sample_map.cc
+++ b/base/metrics/sample_map.cc
@@ -5,6 +5,7 @@
 #include "base/metrics/sample_map.h"
 
 #include "base/logging.h"
+#include "base/stl_util.h"
 
 namespace base {
 
@@ -32,18 +33,16 @@ Count SampleMap::GetCount(Sample value) const {
 
 Count SampleMap::TotalCount() const {
   Count count = 0;
-  for (const auto& entry : sample_counts_) {
+  for (const auto& entry : sample_counts_)
     count += entry.second;
-  }
   return count;
 }
 
 scoped_ptr<SampleCountIterator> SampleMap::Iterator() const {
-  return scoped_ptr<SampleCountIterator>(new SampleMapIterator(sample_counts_));
+  return make_scoped_ptr(new SampleMapIterator(sample_counts_));
 }
 
-bool SampleMap::AddSubtractImpl(SampleCountIterator* iter,
-                                HistogramSamples::Operator op) {
+bool SampleMap::AddSubtractImpl(SampleCountIterator* iter, Operator op) {
   Sample min;
   Sample max;
   Count count;
@@ -77,18 +76,17 @@ void SampleMapIterator::Next() {
 
 void SampleMapIterator::Get(Sample* min, Sample* max, Count* count) const {
   DCHECK(!Done());
-  if (min != NULL)
+  if (min)
     *min = iter_->first;
-  if (max != NULL)
+  if (max)
     *max = iter_->first + 1;
-  if (count != NULL)
+  if (count)
     *count = iter_->second;
 }
 
 void SampleMapIterator::SkipEmptyBuckets() {
-  while (!Done() && iter_->second == 0) {
+  while (!Done() && iter_->second == 0)
     ++iter_;
-  }
 }
 
 }  // namespace base