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

components/metrics/metrics_provider.h

Index: components/metrics/metrics_provider.h
diff --git a/components/metrics/metrics_provider.h b/components/metrics/metrics_provider.h
index 569b1e8fe185df71cfa0dd3ec37711acbbc6a453..77a64567f499463ec21ae923dcee5c0167d3f760 100644
--- a/components/metrics/metrics_provider.h
+++ b/components/metrics/metrics_provider.h
@@ -7,6 +7,12 @@
 
 #include "base/macros.h"
 
+namespace base {
+

[grt (UTC plus 2), 2016/02/08 18:09:19]

nit: omit empty lines for a single forward decl like this

[bcwhite, 2016/02/09 21:08:46]

Done.

+class HistogramSnapshotManager;
+
+}  // namespace base
+
 namespace metrics {
 
 class ChromeUserMetricsExtension;
@@ -63,6 +69,12 @@ class MetricsProvider {
   virtual void ProvideGeneralMetrics(
       ChromeUserMetricsExtension* uma_proto);
 
+  // Called during collection to explicitly load histogram snapshots using a
+  // snapshot manager. PrepareDeltas() will have been already called and

[grt (UTC plus 2), 2016/02/08 18:09:19]

nit "will have already been called"

[bcwhite, 2016/02/09 21:08:46]

Done.

+  // FinishDeltas() will be called later; calls to only PrepareDelta(), not
+  // PrepareDeltas (plural), should be made.
+  virtual void RecordHistogramSnapshots(base::HistogramSnapshotManager* hsm);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(MetricsProvider);
 };