[iOS] Create teardownUI method for SignedInAccountsViewController

SignedInAccountsViewController needs to be torn down and set all
services to null, during UI shutdown.
This patch needs to be cherry-picked in M115.

(cherry picked from commit 79f214a)

Fixed: 1447447
Change-Id: Ic5a408ad1cb419cde9c5742890f392e5bcd353a7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4580009
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Auto-Submit: Jérôme Lebel <jlebel@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1152572}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4604748
Cr-Commit-Position: refs/branch-heads/5790@{#530}
Cr-Branched-From: 1d71a33-refs/heads/main@{#1148114}

ios/chrome/browser/shared/coordinator/scene/scene_controller.mm

@@ -250,6 +250,9 @@ @interface SceneController () <AppStateObserver,
   std::unique_ptr<WebStateListObserverBridge> _webStateListForwardingObserver;
   std::unique_ptr<PolicyWatcherBrowserAgentObserverBridge>
       _policyWatcherObserverBridge;
+  // View controller presents the signed in accounts when they have changed
+  // while the application was in background.
+  __weak SignedInAccountsViewController* _accountsViewController;
 }
 
 // Navigation View controller for the settings.
@@ -1167,6 +1170,9 @@ - (void)teardownUI {
     return;  // Nothing to do.
   }
 
+  [_accountsViewController teardownUI];
+  _accountsViewController = nil;
+
   // The UI should be stopped before the models they observe are stopped.
   // SigninCoordinator teardown is performed by the `signinCompletion` on
   // termination of async events, do not add additional teardown here.
@@ -2920,14 +2926,15 @@ - (void)presentSignedInAccountsViewControllerForBrowserState:
   id<ApplicationSettingsCommands> settingsHandler =
       HandlerForProtocol(self.mainInterface.browser->GetCommandDispatcher(),
                          ApplicationSettingsCommands);
-  UIViewController* accountsViewController =
+  SignedInAccountsViewController* accountsViewController =
       [[SignedInAccountsViewController alloc]
           initWithBrowserState:browserState
                     dispatcher:settingsHandler];
   [[self topPresentedViewController]
       presentViewController:accountsViewController
                    animated:YES
                  completion:nil];
+  _accountsViewController = accountsViewController;
 }
 
 // Close Settings, or Signin or the 3rd-party intents Incognito interstitial.

ios/chrome/browser/ui/authentication/signed_in_accounts/signed_in_accounts_table_view_controller.h

@@ -18,6 +18,9 @@ class ChromeBrowserState;
     NS_DESIGNATED_INITIALIZER;
 - (instancetype)initWithStyle:(UITableViewStyle)style NS_UNAVAILABLE;
 
+// Called when the UI will be torn down.
+- (void)teardownUI;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_AUTHENTICATION_SIGNED_IN_ACCOUNTS_SIGNED_IN_ACCOUNTS_TABLE_VIEW_CONTROLLER_H_

ios/chrome/browser/ui/authentication/signed_in_accounts/signed_in_accounts_table_view_controller.mm

@@ -58,6 +58,11 @@ new ChromeAccountManagerServiceObserverBridge(self,
   return self;
 }
 
+- (void)teardownUI {
+  _accountManagerServiceObserver.reset();
+  _accountManagerService = nullptr;
+}
+
 #pragma mark - UIViewController
 
 - (void)viewDidLoad {

ios/chrome/browser/ui/authentication/signed_in_accounts/signed_in_accounts_view_controller.h

@@ -27,6 +27,9 @@ class ChromeBrowserState;
 
 - (instancetype)initWithCoder:(NSCoder*)coder NS_UNAVAILABLE;
 
+// Called when the UI will be torn down.
+- (void)teardownUI;
+
 @end
 
 #endif  // IOS_CHROME_BROWSER_UI_AUTHENTICATION_SIGNED_IN_ACCOUNTS_SIGNED_IN_ACCOUNTS_VIEW_CONTROLLER_H_

ios/chrome/browser/ui/authentication/signed_in_accounts/signed_in_accounts_view_controller.mm

@@ -117,6 +117,11 @@ - (void)dealloc {
                 forControlEvents:UIControlEventTouchDown];
 }
 
+- (void)teardownUI {
+  [_accountTableView teardownUI];
+  _browserState = nullptr;
+}
+
 #pragma mark UIViewController
 
 - (CGSize)preferredContentSize {