Add the "virtual" keyword on method overrides that are missing it.

net/base/directory_lister.h

 // Copyright (c) 2010 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 NET_BASE_DIRECTORY_LISTER_H_
 #define NET_BASE_DIRECTORY_LISTER_H_
 #pragma once
 
 #include <vector>
 
@@ skipping 64 matching lines @@
   // Call this method to asynchronously stop directory enumeration.  The
   // delegate will receive the OnListDone notification with an error code of
   // net::ERR_ABORTED.
   void Cancel();
 
   // The delegate pointer may be modified at any time.
   DirectoryListerDelegate* delegate() const { return delegate_; }
   void set_delegate(DirectoryListerDelegate* d) { delegate_ = d; }
 
   // PlatformThread::Delegate implementation
-  void ThreadMain();
+  virtual void ThreadMain();
 
  private:
   friend class base::RefCountedThreadSafe<DirectoryLister>;
   friend class DirectoryDataEvent;
 
   // Comparison methods for sorting, chosen based on |sort_|.
   static bool CompareAlphaDirsFirst(const DirectoryListerData& a,
                                     const DirectoryListerData& b);
   static bool CompareDate(const DirectoryListerData& a,
                           const DirectoryListerData& b);
@@ skipping 10 matching lines @@
   DirectoryListerDelegate* delegate_;
   SORT_TYPE sort_;
   MessageLoop* message_loop_;
   PlatformThreadHandle thread_;
   base::CancellationFlag canceled_;
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_DIRECTORY_LISTER_H_