MD Settings: Convert C++ handlers to be JavaScript-lifecycle aware.

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

 // Copyright 2015 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_DEFAULT_BROWSER_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_DEFAULT_BROWSER_HANDLER_H_
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 14 matching lines @@
 // The application used by the OS to open web documents (e.g. *.html)
 // is the "default browser".  This class is an API for the JavaScript
 // settings code to change the default browser settings.
 class DefaultBrowserHandler : public SettingsPageUIHandler {
  public:
   explicit DefaultBrowserHandler(content::WebUI* webui);
   ~DefaultBrowserHandler() override;
 
   // SettingsPageUIHandler implementation.
   void RegisterMessages() override;
+  void OnJavascriptAllowed() override;
+  void OnJavascriptDisallowed() override;
 
  private:
   // Called from WebUI to request the current state.
   void RequestDefaultBrowserState(const base::ListValue* args);
 
   // Makes this the default browser. Called from WebUI.
   void SetAsDefaultBrowser(const base::ListValue* args);
 
   // Called with the default browser state when the DefaultBrowserWorker is
   // done.
   void OnDefaultBrowserWorkerFinished(
       shell_integration::DefaultWebClientState state);
 
   // Reference to a background worker that handles default browser settings.
   scoped_refptr<shell_integration::DefaultBrowserWorker>
       default_browser_worker_;
 
   // Policy setting to determine if default browser setting is managed.
   BooleanPrefMember default_browser_policy_;
 
   // Used to invalidate the DefaultBrowserWorker callback.
   base::WeakPtrFactory<DefaultBrowserHandler> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DefaultBrowserHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_SETTINGS_DEFAULT_BROWSER_HANDLER_H_