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

base/metrics/histogram_snapshot_manager.h

Index: base/metrics/histogram_snapshot_manager.h
diff --git a/base/metrics/histogram_snapshot_manager.h b/base/metrics/histogram_snapshot_manager.h
index c105e8a1d3e7f9ef042debba39d8ce2fdcda3bba..46cf2417d8effaaf446d76d4a12e822c545ae290 100644
--- a/base/metrics/histogram_snapshot_manager.h
+++ b/base/metrics/histogram_snapshot_manager.h
@@ -9,6 +9,7 @@
 
 #include <map>
 #include <string>
+#include <vector>
 
 #include "base/gtest_prod_util.h"
 #include "base/macros.h"
@@ -61,9 +62,14 @@ class BASE_EXPORT HistogramSnapshotManager {
   // until FinishDeltas() completes. PrepareAbsolute() works the same
   // but assumes there were no previous logged values and no future deltas
   // will be created (and thus can work on read-only histograms).
+  // Use Prepare*TakingOwnership() if it is desireable to have this class
+  // automatically delete the histogram once it is "finished".
   void StartDeltas();
   void PrepareDelta(HistogramBase* histogram);
+  void PrepareDeltaTakingOwnership(scoped_ptr<HistogramBase> histogram);
   void PrepareAbsolute(const HistogramBase* histogram);
+  void PrepareAbsoluteTakingOwnership(
+      scoped_ptr<const HistogramBase> histogram);
   void FinishDeltas();
 
  private:
@@ -75,30 +81,27 @@ class BASE_EXPORT HistogramSnapshotManager {
   // information that must persist from one report to the next, such as
   // the "inconsistencies".
   struct SampleInfo {
-    SampleInfo() : histogram(nullptr),
-                   accumulated_samples(nullptr),
-                   inconsistencies(0) {}
-
     // A histogram associated with this sample; it may be one of many if
     // several have been aggregated into the same "accumulated" sample set.
     // Ownership of the histogram remains elsewhere and this pointer is
     // cleared by FinishDeltas().
-    const HistogramBase* histogram;
+    const HistogramBase* histogram = nullptr;
 
     // The current snapshot-delta values being accumulated.
     // TODO(bcwhite): Change this to a scoped_ptr once all build architectures
     // support such as the value of a std::map.
-    HistogramSamples* accumulated_samples;
+    HistogramSamples* accumulated_samples = nullptr;
 
     // The set of inconsistencies (flags) already seen for the histogram.
     // See HistogramBase::Inconsistency for values.
-    unsigned inconsistencies;
+    unsigned inconsistencies = 0;

[grt (UTC plus 2), 2016/02/18 16:44:07]

this should explicitly be uint3_t or another sized type. "unsigned" is banned
based on my read of
https://google.github.io/styleguide/cppguide.html#Integer_Types.

[bcwhite, 2016/02/18 19:35:01]

Done.

   };
 
   // Capture and hold samples from a histogram. This does all the heavy
   // lifting for PrepareDelta() and PrepareAbsolute().
   void PrepareSamples(const HistogramBase* histogram,
-                      scoped_ptr<HistogramSamples> samples);
+                      scoped_ptr<HistogramSamples> samples,
+                      bool take_ownership);
 
   // Try to detect and fix count inconsistency of logged samples.
   void InspectLoggedSamplesInconsistency(
@@ -109,6 +112,10 @@ class BASE_EXPORT HistogramSnapshotManager {
   // by the hash of the histogram name.
   std::map<uint64_t, SampleInfo> known_histograms_;
 
+  // Collection of histograms of which ownership has been passed to this
+  // object. They will be deleted by FinishDeltas().
+  std::vector<scoped_ptr<const HistogramBase>> owned_histograms_;
+
   // Indicates if deltas are currently being prepared.
   bool preparing_deltas_;