WebUI: Add JavaScript lifecycle-control to WebUIMessageHandler.

chrome/browser/ui/webui/settings/settings_page_ui_handler.h

 // Copyright 2016 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_UI_WEBUI_SETTINGS_SETTINGS_PAGE_UI_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_PAGE_UI_HANDLER_H_
 
 #include "base/macros.h"
 #include "base/values.h"
 #include "content/public/browser/web_ui_message_handler.h"
 
 namespace settings {
 
 // The base class handler of Javascript messages of settings pages.
 class SettingsPageUIHandler : public content::WebUIMessageHandler {
  public:
   SettingsPageUIHandler();
   ~SettingsPageUIHandler() override;
 
-  // WebUIMessageHandler implementation.
-  void RegisterMessages() override {}
-
  protected:
   // Helper method for responding to JS requests initiated with
   // cr.sendWithPromise(), for the case where the returned promise should be
   // resolved (request succeeded).
   void ResolveJavascriptCallback(const base::Value& callback_id,
                                  const base::Value& response);
 
   // Helper method for responding to JS requests initiated with
   // cr.sendWithPromise(), for the case where the returned promise should be
   // rejected (request failed).
   void RejectJavascriptCallback(const base::Value& callback_id,
                                 const base::Value& response);
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SettingsPageUIHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_PAGE_UI_HANDLER_H_