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

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

Index: ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm
diff --git a/ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm b/ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm
index d68a3397bdcfeefb187ce72836dc081b86ce877e..d6ca97753a4e3354d309afbf395d3f06d9a4c787 100644
--- a/ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm
+++ b/ios/public/provider/chrome/browser/signin/fake_chrome_identity_service.mm
@@ -24,8 +24,7 @@ void FakeGetAccessToken(ChromeIdentity*,
                         const std::string&,
                         const std::set<std::string>&,
                         const ios::AccessTokenCallback& callback) {
-  base::mac::ScopedBlock<ios::AccessTokenCallback> safe_callback(
-      [callback copy]);
+  ios::AccessTokenCallback safe_callback = [callback copy];
 
   // |GetAccessToken| is normally an asynchronous operation (that requires some
   // network calls), this is replicated here by dispatching it.
@@ -37,7 +36,7 @@ void FakeGetAccessToken(ChromeIdentity*,
     NSDate* expiresDate = [NSDate dateWithTimeIntervalSinceNow:expiration];
     NSString* token = [expiresDate description];
 
-    safe_callback.get()(token, expiresDate, nil);
+    safe_callback(token, expiresDate, nil);
   });
 }
 
@@ -71,7 +70,7 @@ void FakeGetHostedDomainForIdentity(ChromeIdentity* identity,
 
 @interface FakeAccountDetailsViewController : UIViewController {
   ChromeIdentity* _identity;  // Weak.
-  base::scoped_nsobject<UIButton> _removeAccountButton;
+  UIButton* _removeAccountButton;
 }
 @end
 
@@ -98,8 +97,7 @@ void FakeGetHostedDomainForIdentity(ChromeIdentity* identity,
   // Obnoxious color, this is a test screen.
   self.view.backgroundColor = [UIColor orangeColor];
 
-  _removeAccountButton.reset(
-      [[UIButton buttonWithType:UIButtonTypeCustom] retain]);
+  _removeAccountButton = [[UIButton buttonWithType:UIButtonTypeCustom] retain];
   [_removeAccountButton setTitle:@"Remove account"
                         forState:UIControlStateNormal];
   [_removeAccountButton addTarget:self
@@ -146,8 +144,8 @@ base::scoped_nsobject<UINavigationController>
 FakeChromeIdentityService::NewAccountDetails(
     ChromeIdentity* identity,
     id<ChromeIdentityBrowserOpener> browser_opener) {
-  base::scoped_nsobject<UIViewController> accountDetailsViewController(
-      [[FakeAccountDetailsViewController alloc] initWithIdentity:identity]);
+  UIViewController* accountDetailsViewController =
+      [[FakeAccountDetailsViewController alloc] initWithIdentity:identity];
   base::scoped_nsobject<UINavigationController> navigationController(
       [[UINavigationController alloc]
           initWithRootViewController:accountDetailsViewController]);