Reorganize histograms for persistence.

base/metrics/histogram.cc

Index: base/metrics/histogram.cc
diff --git a/base/metrics/histogram.cc b/base/metrics/histogram.cc
index b37bc4c4685c5476c9145a81bb953ddfbc2532d5..8913471f6c86b2165e48367fa94e9cde8ef5f943 100644
--- a/base/metrics/histogram.cc
+++ b/base/metrics/histogram.cc
@@ -18,6 +18,7 @@
 #include "base/debug/alias.h"
 #include "base/logging.h"
 #include "base/metrics/histogram_macros.h"
+#include "base/metrics/metrics_hashes.h"
 #include "base/metrics/sample_vector.h"
 #include "base/metrics/statistics_recorder.h"
 #include "base/pickle.h"
@@ -259,6 +260,10 @@ bool Histogram::InspectConstructionArguments(const std::string& name,
   return true;
 }
 
+uint64_t Histogram::id() const {
+  return samples_->id();
+}
+
 HistogramType Histogram::GetHistogramType() const {
   return HISTOGRAM;
 }
@@ -297,6 +302,7 @@ scoped_ptr<HistogramSamples> Histogram::SnapshotSamples() const {
 }
 
 void Histogram::AddSamples(const HistogramSamples& samples) {
+  DCHECK(samples.id() == 0 || samples.id() == samples_->id());
   samples_->Add(samples);
 }
 
@@ -335,7 +341,7 @@ Histogram::Histogram(const std::string& name,
     declared_min_(minimum),
     declared_max_(maximum) {
   if (ranges)
-    samples_.reset(new SampleVector(ranges));
+    samples_.reset(new SampleVector(metrics::HashMetricName(name), ranges));
 }
 
 Histogram::~Histogram() {
@@ -392,7 +398,9 @@ HistogramBase* Histogram::DeserializeInfoImpl(PickleIterator* iter) {
 }
 
 scoped_ptr<SampleVector> Histogram::SnapshotSampleVector() const {
-  scoped_ptr<SampleVector> samples(new SampleVector(bucket_ranges()));
+  scoped_ptr<SampleVector> samples(
+      new SampleVector(metrics::HashMetricName(histogram_name()),
+                       bucket_ranges()));
   samples->Add(*samples_);
   return samples.Pass();
 }