GTTF: Add missing virtual destructors.

chrome/browser/download/download_danger_prompt.h

 // Copyright (c) 2012 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_DOWNLOAD_DOWNLOAD_DANGER_PROMPT_H_
 #define CHROME_BROWSER_DOWNLOAD_DOWNLOAD_DANGER_PROMPT_H_
 
 #include "base/callback_forward.h"
 
 namespace content {
@@ skipping 27 matching lines @@
   static DownloadDangerPrompt* Create(
       content::DownloadItem* item,
       content::WebContents* web_contents,
       bool show_context,
       const base::Closure& accepted,
       const base::Closure& canceled);
 
  protected:
   friend class DownloadDangerPromptTest;
 
+  virtual ~DownloadDangerPrompt() { }
+
   // Only to be used by tests. Subclasses must override to manually call the
   // respective button click handler.
   virtual void InvokeActionForTesting(Action action) = 0;
 };
 
 #endif  // CHROME_BROWSER_DOWNLOAD_DOWNLOAD_DANGER_PROMPT_H_