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

components/signin/ios/browser/oauth2_token_service_observer_bridge.mm

 // Copyright 2014 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.
 
 #include "components/signin/ios/browser/oauth2_token_service_observer_bridge.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 OAuth2TokenServiceObserverBridge::OAuth2TokenServiceObserverBridge(
     OAuth2TokenService* token_service,
     id<OAuth2TokenServiceObserverBridgeDelegate> delegate)
         : token_service_(token_service),
           delegate_(delegate) {
     DCHECK(token_service_);
     token_service_->AddObserver(this);
 }
 OAuth2TokenServiceObserverBridge::~OAuth2TokenServiceObserverBridge() {
   token_service_->RemoveObserver(this);
@@ skipping 22 matching lines @@
     [delegate_ onStartBatchChanges];
   }
 
 }
 
 void OAuth2TokenServiceObserverBridge::OnEndBatchChanges() {
   if ([delegate_ respondsToSelector:@selector(onEndBatchChanges)]) {
     [delegate_ onEndBatchChanges];
   }
 }