In sync passphrase dialog reset left bar button and title to saved values

ios/chrome/browser/ui/settings/sync_encryption_passphrase_collection_view_controller.mm

 // 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.
 
 #import "ios/chrome/browser/ui/settings/sync_encryption_passphrase_collection_view_controller.h"
 
 #include <memory>
 
 #include "base/i18n/time_formatting.h"
 #include "base/mac/foundation_util.h"
@@ skipping 412 matching lines @@
   self.navigationItem.leftBarButtonItem = [self spinnerButton];
   savedTitle_ = [self.title copy];
   self.title = processingMessage_;
 }
 
 - (void)hideDecryptionProgress {
   if (!isDecryptionProgressShown_)
     return;
   isDecryptionProgressShown_ = NO;
 
-  self.navigationItem.leftBarButtonItem = savedLeftButton_ = nil;
-  self.title = savedTitle_ = nil;
+  self.navigationItem.leftBarButtonItem = savedLeftButton_;
+  savedLeftButton_ = nil;
+  self.title = savedTitle_;
+  savedTitle_ = nil;
   [self setRightNavBarItem];
 }
 
 - (void)registerTextField:(UITextField*)textField {
   [textField addTarget:self
                 action:@selector(textFieldDidBeginEditing:)
       forControlEvents:UIControlEventEditingDidBegin];
   [textField addTarget:self
                 action:@selector(textFieldDidChange:)
       forControlEvents:UIControlEventEditingChanged];
@@ skipping 120 matching lines @@
       self.navigationController) popViewControllerOrCloseSettingsAnimated:NO];
 }
 
 #pragma mark - SettingsControllerProtocol callbacks
 
 - (void)settingsWillBeDismissed {
   [self stopObserving];
 }
 
 @end