Persist setup metrics and have Chrome report them during UMA upload.

base/metrics/histogram_snapshot_manager.cc

Index: base/metrics/histogram_snapshot_manager.cc
diff --git a/base/metrics/histogram_snapshot_manager.cc b/base/metrics/histogram_snapshot_manager.cc
index f641d44f1154bff8d15930b94f93caa93b1298d0..7778ca09ce5330458f7b8399eb50cdfb02809339 100644
--- a/base/metrics/histogram_snapshot_manager.cc
+++ b/base/metrics/histogram_snapshot_manager.cc
@@ -31,6 +31,8 @@ void HistogramSnapshotManager::StartDeltas() {
   DCHECK(!preparing_deltas_);
   preparing_deltas_ = true;
 
+  DCHECK(owned_histograms_.empty());
+
 #ifdef DEBUG
   for (auto iter : known_histograms) {
     CHECK(!iter->second.histogram);
@@ -41,26 +43,46 @@ void HistogramSnapshotManager::StartDeltas() {
 }
 
 void HistogramSnapshotManager::PrepareDelta(HistogramBase* histogram) {
-  PrepareSamples(histogram, histogram->SnapshotDelta());
+  PrepareSamples(histogram, histogram->SnapshotDelta(), false);
+}
+
+void HistogramSnapshotManager::PrepareDeltaTakingOwnership(
+    HistogramBase* histogram) {
+  PrepareSamples(histogram, histogram->SnapshotDelta(), true);
 }
 
 void HistogramSnapshotManager::PrepareOnce(const HistogramBase* histogram) {
-  PrepareSamples(histogram, histogram->SnapshotSamples());
+  PrepareSamples(histogram, histogram->SnapshotSamples(), false);
+}
+
+void HistogramSnapshotManager::PrepareOnceTakingOwnership(
+    const HistogramBase* histogram) {
+  PrepareSamples(histogram, histogram->SnapshotSamples(), true);
 }
 
 void HistogramSnapshotManager::PrepareSamples(
     const HistogramBase* histogram,
-    scoped_ptr<HistogramSamples> samples) {
+    scoped_ptr<HistogramSamples> samples,
+    bool take_ownership) {
   DCHECK(histogram_flattener_);
+  scoped_ptr<const HistogramBase> owned_histogram;
 
   // Get information known about this histogram.
   SampleInfo* sample_info = &known_histograms_[histogram->name_hash()];
   if (sample_info->histogram) {
     DCHECK_EQ(sample_info->histogram->histogram_name(),
               histogram->histogram_name()) << "hash collision";
+    // Passed histogram won't be needed past end of this method so store
+    // it in a scoped_ptr that will release it when returning.
+    if (take_ownership)
+      owned_histogram.reset(histogram);
   } else {
     // First time this histogram has been seen; datafill.
     sample_info->histogram = histogram;
+    // The histogram data will be needed up until "finished" so store
+    // in member vector for releasing when that is done.
+    if (take_ownership)
+      owned_histograms_.push_back(histogram);
   }
 
   // Crash if we detect that our histograms have been overwritten.  This may be
@@ -131,6 +153,10 @@ void HistogramSnapshotManager::FinishDeltas() {
     sample_info->histogram = nullptr;
   }
 
+  STLDeleteContainerPointers(owned_histograms_.begin(),
+                             owned_histograms_.end());
+  owned_histograms_.clear();
+
   preparing_deltas_ = false;
 }