Access SigninErrorProvider through ChromeBrowserProvider.

ios/chrome/browser/signin/profile_oauth2_token_service_ios_provider_impl.mm

 // Copyright 2016 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 "ios/chrome/browser/signin/profile_oauth2_token_service_ios_provider_impl.h"
 
 #include "base/logging.h"
 #include "base/strings/sys_string_conversions.h"
 #include "ios/chrome/browser/signin/constants.h"
 #include "ios/chrome/browser/signin/signin_util.h"
@@ skipping 62 matching lines @@
     return kAuthenticationErrorCategoryUnknownIdentityErrors;
   }
 
   ios::ChromeIdentityService* identity_service =
       ios::GetChromeBrowserProvider()->GetChromeIdentityService();
   if (identity_service->IsMDMError(
           identity_service->GetIdentityWithGaiaID(gaia_id), error)) {
     return kAuthenticationErrorCategoryAuthorizationErrors;
   }
 
-  ios::SigninErrorCategory error_category =
-      ios::GetSigninErrorProvider()->GetErrorCategory(error);
-  switch (error_category) {
+  ios::SigninErrorProvider* provider =
+      ios::GetChromeBrowserProvider()->GetSigninErrorProvider();
+  switch (provider->GetErrorCategory(error)) {
     case ios::SigninErrorCategory::UNKNOWN_ERROR: {
       // Google's OAuth 2 implementation returns a 400 with JSON body
       // containing error key "invalid_grant" to indicate the refresh token
       // is invalid or has been revoked by the user.
       // Check that the underlying library does not categorize these errors as
       // unknown.
-      NSString* json_error_key =
-          ios::GetSigninErrorProvider()->GetInvalidGrantJsonErrorKey();
-      DCHECK(!ios::GetSigninErrorProvider()->IsBadRequest(error) ||
+      NSString* json_error_key = provider->GetInvalidGrantJsonErrorKey();
+      DCHECK(!provider->IsBadRequest(error) ||
              ![[[error userInfo] valueForKeyPath:@"json.error"]
                  isEqual:json_error_key]);
       return kAuthenticationErrorCategoryUnknownErrors;
     }
     case ios::SigninErrorCategory::AUTHORIZATION_ERROR:
-      if (ios::GetSigninErrorProvider()->IsForbidden(error)) {
+      if (provider->IsForbidden(error)) {
         return kAuthenticationErrorCategoryAuthorizationForbiddenErrors;
       }
       return kAuthenticationErrorCategoryAuthorizationErrors;
     case ios::SigninErrorCategory::NETWORK_ERROR:
       return kAuthenticationErrorCategoryNetworkServerErrors;
     case ios::SigninErrorCategory::USER_CANCELLATION_ERROR:
       return kAuthenticationErrorCategoryUserCancellationErrors;
   }
 }