Support saving browser metrics to disk and reading them during next run.

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 {
@@ skipping 52 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 already been called and
-  // FinishDeltas() will be called later; calls to only PrepareDelta(), not
-  // PrepareDeltas (plural), should be made.
+  // Called during regular collection to explicitly load histogram snapshots
+  // using a snapshot manager. PrepareDeltas() will have already been called
+  // and FinishDeltas() will be called later; calls to only PrepareDelta(),
+  // not PrepareDeltas (plural), should be made.
   virtual void RecordHistogramSnapshots(
       base::HistogramSnapshotManager* snapshot_manager);
 
+  // Called during collection of initial metrics to explicitly load histogram
+  // snapshots using a snapshot manager. PrepareDeltas() will have already
+  // been called and FinishDeltas() will be called later; calls to only
+  // PrepareDelta(), not PrepareDeltas (plural), should be made.
+  virtual void RecordInitialHistogramSnapshots(
+      base::HistogramSnapshotManager* snapshot_manager);
+
  private:
   DISALLOW_COPY_AND_ASSIGN(MetricsProvider);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_METRICS_PROVIDER_H_