[CRD iOS] Refactor an interface for RemotingAuthorization

remoting/ios/app/app_view_controller.h

 // Copyright 2017 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 REMOTING_IOS_APP_APP_VIEW_CONTROLLER_H_
 #define REMOTING_IOS_APP_APP_VIEW_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
+@protocol RemotingAuthentication;
+
 @protocol AppController<NSObject>
 
 // For adding new methods, please mark them as optional until they are
 // implemented in both Chromium and ios_internal. For deletion, just reverse the
 // procedure. This is to prevent build break in internal buildbot.
 
 - (void)showMenuAnimated:(BOOL)animated;
 - (void)hideMenuAnimated:(BOOL)animated;
 - (void)presentSignInFlow;
 
+@property(nonatomic, readonly) id<RemotingAuthentication> authentication;
+@property(nonatomic) UIViewController* mainViewController;
+
 @end
 
 // The root view controller of the app. It acts as a container controller for
 // |mainViewController|, which will be shown as the primary content of the view.
 // Implementation can add drawer or modal for things like the side menu or help
 // and feedback.
 @interface AppViewController : UIViewController<AppController>
 
-- (instancetype)initWithMainViewController:
-    (UIViewController*)mainViewController;
-
 @end
 
 #endif  // REMOTING_IOS_APP_APP_VIEW_CONTROLLER_H_