[CRD iOS] Use UINavigationController for view stack manipulation

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 282 matching lines @@
   _activityIndicator.hidden = NO;
   _activityIndicator.indicatorMode = MDCActivityIndicatorModeDeterminate;
   _activityIndicator.cycleColors = @[ [UIColor greenColor] ];
   [_activityIndicator startAnimating];
   _activityIndicator.progress = 1.0;
 
   HostViewController* hostViewController =
       [[HostViewController alloc] initWithClient:_client];
   _client = nil;
 
-  __weak UIViewController* parentController = self.presentingViewController;
-
-  [self dismissViewControllerAnimated:NO
-                           completion:^{
-                             [parentController
-                                 presentViewController:hostViewController
-                                              animated:NO
-                                            completion:nil];
-                           }];
+  // Replaces current (topmost) view controller with |hostViewController|.
+  NSMutableArray* controllers =
+      [self.navigationController.viewControllers mutableCopy];
+  [controllers removeLastObject];
+  [controllers addObject:hostViewController];
+  [self.navigationController setViewControllers:controllers animated:NO];
 }
 
 - (void)didProvidePin:(NSString*)pin createPairing:(BOOL)createPairing {
   // TODO(nicholss): There is an open question if createPairing is supported on
   // iOS. Need to fingure this out.
   [[NSNotificationCenter defaultCenter]
       postNotificationName:kHostSessionPinProvided
                     object:self
                   userInfo:[NSDictionary dictionaryWithObject:pin
                                                        forKey:kHostSessionPin]];
 }
 
 - (void)didTapCancel:(id)sender {
   _client = nil;
-  [self dismissViewControllerAnimated:YES completion:nil];
+  [self.navigationController popViewControllerAnimated:YES];
 }
 
 - (void)hostSessionStatusChanged:(NSNotification*)notification {
   NSLog(@"hostSessionStatusChanged: %@", [notification userInfo]);
   ClientConnectionViewState state;
   ClientSessionDetails* sessionDetails =
       [[notification userInfo] objectForKey:kSessionDetails];
   switch (sessionDetails.state) {
     case SessionInitializing:
     // Same as HostConnecting in UI. Fall-though.
@@ skipping 16 matching lines @@
     default:
       LOG(ERROR) << "Unknown State for Session, " << sessionDetails.state;
       return;
   }
   [[NSOperationQueue mainQueue] addOperationWithBlock:^{
     [self setState:state];
   }];
 }
 
 @end