Basic UkmService implementation

components/metrics/persisted_logs_metrics_impl.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_PERSISTED_LOGS_METRICS_IMPL_H_
 #define COMPONENTS_METRICS_PERSISTED_LOGS_METRICS_IMPL_H_
 
 #include "base/macros.h"
 #include "components/metrics/persisted_logs_metrics.h"
 
 namespace metrics {
 
 // Implementation for recording metrics from PersistedLogs.
 class PersistedLogsMetricsImpl : public PersistedLogsMetrics {
  public:
   PersistedLogsMetricsImpl() {}
-  ~PersistedLogsMetricsImpl() {}
+  ~PersistedLogsMetricsImpl() override {}
 
   PersistedLogs::LogReadStatus RecordLogReadStatus(
       PersistedLogs::LogReadStatus status) override;
 
   void RecordCompressionRatio(
     size_t compressed_size, size_t original_size) override;
 
   void RecordDroppedLogSize(size_t size) override;
 
   void RecordDroppedLogsNum(int dropped_logs_num) override;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(PersistedLogsMetricsImpl);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_PERSISTED_LOGS_METRICS_IMPL_H_