Virtual destructors should have virtual keyword.

chrome/browser/sync/util/extensions_activity_monitor.h

 // Copyright (c) 2011 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 CHROME_BROWSER_SYNC_UTIL_EXTENSIONS_ACTIVITY_MONITOR_H_
 #define CHROME_BROWSER_SYNC_UTIL_EXTENSIONS_ACTIVITY_MONITOR_H_
 #pragma once
 
 #include <map>
 
@@ skipping 28 matching lines @@
     // How many times the extension successfully invoked a write
     // operation through the bookmarks API since the last CommitMessage.
     uint32 bookmark_write_count;
   };
 
   typedef std::map<std::string, Record> Records;
 
   // Creates an ExtensionsActivityMonitor to monitor extensions activities on
   // BrowserThread::UI.
   ExtensionsActivityMonitor();
-  ~ExtensionsActivityMonitor();
+  virtual ~ExtensionsActivityMonitor();
 
   // Fills |buffer| with snapshot of current records in constant time by
   // swapping.  This is done mutually exclusively w.r.t methods of this class.
   void GetAndClearRecords(Records* buffer);
 
   // Add |records| piece-wise (by extension id) to the set of active records.
   // This is done mutually exclusively w.r.t the methods of this class.
   void PutRecords(const Records& records);
 
   // NotificationObserver implementation.  Called on |ui_loop_|.
   virtual void Observe(NotificationType type,
                        const NotificationSource& source,
                        const NotificationDetails& details);
  private:
   Records records_;
   mutable base::Lock records_lock_;
 
   // Used only from UI loop.
   NotificationRegistrar registrar_;
 };
 
 }  // namespace browser_sync
 
 #endif  // CHROME_BROWSER_SYNC_UTIL_EXTENSIONS_ACTIVITY_MONITOR_H_