Merge histograms from providers into StatisticsRecorder for display.

components/metrics/file_metrics_provider.h

 // Copyright 2016 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_FILE_METRICS_PROVIDER_H_
 #define COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_
 
 #include <list>
 #include <memory>
 #include <string>
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
 #include "base/gtest_prod_util.h"
 #include "base/memory/weak_ptr.h"
+#include "base/metrics/statistics_recorder.h"
 #include "base/threading/thread_checker.h"
 #include "base/time/time.h"
 #include "components/metrics/metrics_provider.h"
 
 class PrefRegistrySimple;
 class PrefService;
 
 namespace base {
 class TaskRunner;
 }
 
 namespace metrics {
 
 // FileMetricsProvider gathers and logs histograms written to files on disk.
 // Any number of files can be registered and will be polled once per upload
 // cycle (at startup and periodically thereafter -- about every 30 minutes
 // for desktop) for data to send.
-class FileMetricsProvider : public MetricsProvider {
+class FileMetricsProvider : public MetricsProvider,
+                            public base::StatisticsRecorder::HistogramProvider {
  public:
   enum SourceType {
     // "Atomic" files are a collection of histograms that are written
     // completely in a single atomic operation (typically a write followed
     // by an atomic rename) and the file is never updated again except to
     // be replaced by a completely new set of histograms. This is the only
     // option that can be used if the file is not writeable by *this*
     // process. Once the file has been read, an attempt will be made to
     // delete it thus providing some measure of safety should different
     // instantiations (such as by different users of a system-level install)
@@ skipping 121 matching lines @@
 
   // Schedules the deletion of a file in the background using the task-runner.
   void DeleteFileAsync(const base::FilePath& path);
 
   // Updates the persistent state information to show a source as being read.
   void RecordSourceAsRead(SourceInfo* source);
 
   // metrics::MetricsDataProvider:
   void OnDidCreateMetricsLog() override;
   bool HasInitialStabilityMetrics() override;
-  void MergeHistogramDeltas() override;
   void RecordInitialHistogramSnapshots(
       base::HistogramSnapshotManager* snapshot_manager) override;
 
+  // base::StatisticsRecorder::HistogramProvider:
+  void MergeHistogramDeltas() override;
+
   // A task-runner capable of performing I/O.
   scoped_refptr<base::TaskRunner> task_runner_;
 
   // A list of sources not currently active that need to be checked for changes.
   SourceInfoList sources_to_check_;
 
   // A list of currently active sources to be merged when required.
   SourceInfoList sources_mapped_;
 
   // A list of sources for a previous run. These are held separately because
   // they are not subject to the periodic background checking that handles
   // metrics for the current run.
   SourceInfoList sources_for_previous_run_;
 
   // The preferences-service used to store persistent state about sources.
   PrefService* pref_service_;
 
   base::ThreadChecker thread_checker_;
   base::WeakPtrFactory<FileMetricsProvider> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(FileMetricsProvider);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_FILE_METRICS_PROVIDER_H_