[ObjC ARC] Converts ios/chrome/browser/signin:test_support to ARC.

ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm

Index: ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm
diff --git a/ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm b/ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm
index 93de808a526ed48bee03504b7827538ec3b4c45a..d4cf71492ba808922492268638fe466ce00993ce 100644
--- a/ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm
+++ b/ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.mm
@@ -5,21 +5,20 @@
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity_interaction_manager.h"
 
 #include "base/mac/scoped_block.h"
-#include "base/mac/scoped_nsobject.h"
 #import "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 #import "ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.h"
 #include "ios/public/provider/chrome/browser/signin/signin_error_provider.h"
 
 @interface FakeAddAccountViewController : UIViewController {
   FakeChromeIdentityInteractionManager* _manager;  // Weak.
-  base::scoped_nsobject<UIButton> _cancelButton;
-  base::scoped_nsobject<UIButton> _signInButton;
+  UIButton* _cancelButton;
+  UIButton* _signInButton;
 }
 @end
 
 @interface FakeChromeIdentityInteractionManager () {
-  base::mac::ScopedBlock<SigninCompletionCallback> _completionCallback;
-  base::scoped_nsobject<UIViewController> _viewController;
+  SigninCompletionCallback _completionCallback;
+  UIViewController* _viewController;
   BOOL _isCanceling;
 }
 
@@ -56,14 +55,14 @@
   // Obnoxious color, this is a test screen.
   self.view.backgroundColor = [UIColor magentaColor];
 
-  _signInButton.reset([[UIButton buttonWithType:UIButtonTypeCustom] retain]);
+  _signInButton = [[UIButton buttonWithType:UIButtonTypeCustom] retain];
   [_signInButton setTitle:@"Sign in" forState:UIControlStateNormal];
   [_signInButton addTarget:self
                     action:@selector(didTapSignIn:)
           forControlEvents:UIControlEventTouchUpInside];
   [self.view addSubview:_signInButton];
 
-  _cancelButton.reset([[UIButton buttonWithType:UIButtonTypeCustom] retain]);
+  _cancelButton = [[UIButton buttonWithType:UIButtonTypeCustom] retain];
   [_cancelButton setTitle:@"Cancel" forState:UIControlStateNormal];
   [_cancelButton setAccessibilityIdentifier:@"cancel"];
   [_cancelButton addTarget:self
@@ -103,9 +102,9 @@
 }
 
 - (void)addAccountWithCompletion:(SigninCompletionCallback)completion {
-  _completionCallback.reset(completion, base::scoped_policy::RETAIN);
-  _viewController.reset(
-      [[FakeAddAccountViewController alloc] initWithInteractionManager:self]);
+  _completionCallback = [completion copy];
+  _viewController =
+      [[FakeAddAccountViewController alloc] initWithInteractionManager:self];
   [self.delegate interactionManager:self
               presentViewController:_viewController
                            animated:YES
@@ -152,13 +151,15 @@
 }
 
 - (void)runCompletionCallbackWithError:(NSError*)error {
-  _viewController.reset();
+  _viewController = nil;
   if (_completionCallback) {
     // Ensure self is not destroyed in the callback.
-    base::scoped_nsobject<FakeChromeIdentityInteractionManager> strongSelf(
-        [self retain]);
-    _completionCallback.get()(error ? nil : _fakeIdentity, error);
-    _completionCallback.reset();
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-variable"
+    FakeChromeIdentityInteractionManager* strongSelf = self;
+#pragma clang diagnostic pop
+    _completionCallback(error ? nil : _fakeIdentity, error);
+    _completionCallback = nil;
   }
 }