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

chrome/browser/extensions/extension_bookmarks_module.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 CHROME_BROWSER_EXTENSIONS_EXTENSION_BOOKMARKS_MODULE_H_
 #define CHROME_BROWSER_EXTENSIONS_EXTENSION_BOOKMARKS_MODULE_H_
 #pragma once
 
 #include <list>
 #include <set>
@@ skipping 161 matching lines @@
 };
 
 class BookmarksIOFunction : public BookmarksFunction,
                             public SelectFileDialog::Listener {
  public:
   BookmarksIOFunction();
   virtual ~BookmarksIOFunction();
 
   // Overridden from SelectFileDialog::Listener:
   virtual void FileSelected(const FilePath& path, int index, void* params) = 0;
-  void MultiFilesSelected(const std::vector<FilePath>& files, void* params);
-  void FileSelectionCanceled(void* params);
+  virtual void MultiFilesSelected(const std::vector<FilePath>& files,
+                                  void* params);
+  virtual void FileSelectionCanceled(void* params);
   void SelectFile(SelectFileDialog::Type type);
 
  protected:
   scoped_refptr<SelectFileDialog> select_file_dialog_;
 };
 
 class ImportBookmarksFunction : public BookmarksIOFunction {
  public:
   // Override BookmarkManagerIOFunction.
-  bool RunImpl();
-  void FileSelected(const FilePath& path, int index, void* params);
+  virtual bool RunImpl();
+  virtual void FileSelected(const FilePath& path, int index, void* params);
 
  private:
   DECLARE_EXTENSION_FUNCTION_NAME("bookmarks.import");
 };
 
 class ExportBookmarksFunction : public BookmarksIOFunction {
  public:
   // Override BookmarkManagerIOFunction.
-  bool RunImpl();
-  void FileSelected(const FilePath& path, int index, void* params);
+  virtual bool RunImpl();
+  virtual void FileSelected(const FilePath& path, int index, void* params);
 
  private:
   DECLARE_EXTENSION_FUNCTION_NAME("bookmarks.export");
 };
 
 #endif  // CHROME_BROWSER_EXTENSIONS_EXTENSION_BOOKMARKS_MODULE_H_