Basic UkmService implementation

components/metrics/persisted_logs.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_PERSISTED_LOGS_H_
 #define COMPONENTS_METRICS_PERSISTED_LOGS_H_
 
 #include <stddef.h>
 
 #include <memory>
@@ skipping 58 matching lines @@
   // Adds a log to the list.
   void StoreLog(const std::string& log_data);
 
   // Stages the most recent log.  The staged_log will remain the same even if
   // additional logs are added.
   void StageLog();
 
   // Remove the staged log.
   void DiscardStagedLog();
 
+  // Delete all logs, in memory and on disk.
+  void Purge();
+
   // True if a log has been staged.
   bool has_staged_log() const { return staged_log_index_ != -1; }
 
   // Returns the element in the front of the list.
   const std::string& staged_log() const {
     DCHECK(has_staged_log());
     return list_[staged_log_index_].compressed_log_data;
   }
 
   // Returns the element in the front of the list.
@@ skipping 65 matching lines @@
   // The index and type of the log staged for upload. If nothing has been
   // staged, the index will be -1.
   int staged_log_index_;
 
   DISALLOW_COPY_AND_ASSIGN(PersistedLogs);
 };
 
 }  // namespace metrics
 
 #endif  // COMPONENTS_METRICS_PERSISTED_LOGS_H_