[MD settings] lighter weight initializer for protocol handler enabled messages

chrome/browser/ui/webui/settings/protocol_handlers_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_PROTOCOL_HANDLERS_HANDLER_H_
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_PROTOCOL_HANDLERS_HANDLER_H_
 
 #include <string>
 
 #include "base/macros.h"
@@ skipping 26 matching lines @@
   void OnJavascriptAllowed() override;
   void OnJavascriptDisallowed() override;
   void RegisterMessages() override;
 
   // content::NotificationObserver:
   void Observe(int type,
                const content::NotificationSource& source,
                const content::NotificationDetails& details) override;
 
  private:
-  // Called to fetch the initial list of data to show.
+  // Called to fetch the initial list of data to show. If the full list of
+  // handlers is not needed, consider using HandleInitializeUpdates instead.
   void HandleInitializeList(const base::ListValue* args);
 
+  // Called to begin updates to the handlers enabled status. This is a subset
+  // (lighter alternative) of HandleInitializeList. There's no need to call this
+  // function if HandleInitializeList is called.
+  void HandleInitializeUpdates(const base::ListValue* args);
+
   // Notifies the JS side whether the handlers are enabled or not.
   void SendHandlersEnabledValue();
 
   // Called when the user toggles whether custom handlers are enabled.
   void HandleSetHandlersEnabled(const base::ListValue* args);
 
   // Called when the user sets a new default handler for a protocol.
   void HandleSetDefault(const base::ListValue* args);
 
   // Called when the user clears the default handler for a protocol.
@@ skipping 26 matching lines @@
   ProtocolHandlerRegistry* GetProtocolHandlerRegistry();
 
   content::NotificationRegistrar notification_registrar_;
 
   DISALLOW_COPY_AND_ASSIGN(ProtocolHandlersHandler);
 };
 
 }  // namespace settings
 
 #endif  // CHROME_BROWSER_UI_WEBUI_SETTINGS_PROTOCOL_HANDLERS_HANDLER_H_