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

components/metrics/metrics_provider.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_METRICS_METRICS_PROVIDER_H_
 #define COMPONENTS_METRICS_METRICS_PROVIDER_H_
 
 #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;
 class SystemProfileProto;
 class SystemProfileProto_Stability;
 
 // MetricsProvider is an interface allowing different parts of the UMA protos to
 // be filled out by different classes.
 class MetricsProvider {
  public:
@@ skipping 36 matching lines @@
   // Called to indicate that saved stability prefs should be cleared, e.g.
   // because they are from an old version and should not be kept.
   virtual void ClearSavedStabilityMetrics();
 
   // Provides general metrics that are neither system profile nor stability
   // metrics. May also be used to add histograms when final metrics are
   // collected right before upload.
   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);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_PROVIDER_H_