[CRD iOS] Refactor an interface for RemotingAuthorization

remoting/ios/app/client_connection_view_controller.mm

 // 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.
 
 #if !defined(__has_feature) || !__has_feature(objc_arc)
 #error "This file requires ARC support."
 #endif
 
 #import "remoting/ios/app/client_connection_view_controller.h"
 
@@ skipping 42 matching lines @@
 @implementation ClientConnectionViewController
 
 @synthesize state = _state;
 
 - (instancetype)initWithHostInfo:(HostInfo*)hostInfo {
   self = [super init];
   if (self) {
     _client = [[RemotingClient alloc] init];
 
     __weak RemotingClient* weakClient = _client;
-    [[RemotingService SharedInstance].authentication
-        callbackWithAccessToken:base::BindBlockArc(^(
-                                    remoting::OAuthTokenGetter::Status status,
-                                    const std::string& user_email,
-                                    const std::string& access_token) {
+    [RemotingService.instance.authentication
+        callbackWithAccessToken:^(RemotingAuthenticationStatus status,
+                                  NSString* userEmail, NSString* accessToken) {
           [weakClient connectToHost:hostInfo
-                           username:base::SysUTF8ToNSString(user_email)
-                        accessToken:base::SysUTF8ToNSString(access_token)];
-        })];
+                           username:userEmail
+                        accessToken:accessToken];
+        }];
 
     _remoteHostName = hostInfo.hostName;
 
     // TODO(yuweih): This logic may be reused by other views.
     UIButton* cancelButton = [UIButton buttonWithType:UIButtonTypeSystem];
     [cancelButton setTitle:@"CANCEL" forState:UIControlStateNormal];
     [cancelButton
         setImage:[RemotingTheme
                          .backIcon imageFlippedForRightToLeftLayoutDirection]
         forState:UIControlStateNormal];
@@ skipping 274 matching lines @@
     default:
       LOG(ERROR) << "Unknown State for Session, " << sessionDetails.state;
       return;
   }
   [[NSOperationQueue mainQueue] addOperationWithBlock:^{
     [self setState:state];
   }];
 }
 
 @end