Remove old getter/setter for SigninErrorProvider.

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

 // Copyright 2015 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/public/provider/chrome/browser/signin/signin_error_provider.h"
 
 namespace ios {
 
-namespace {
-SigninErrorProvider* g_signin_error_provider = nullptr;
-}
-
-void SetSigninErrorProvider(SigninErrorProvider* provider) {
-  g_signin_error_provider = provider;
-}
-
-SigninErrorProvider* GetSigninErrorProvider() {
-  return g_signin_error_provider;
-}
-
 SigninErrorProvider::SigninErrorProvider() {}
 
 SigninErrorProvider::~SigninErrorProvider() {}
 
 SigninErrorCategory SigninErrorProvider::GetErrorCategory(NSError* error) {
   return SigninErrorCategory::UNKNOWN_ERROR;
 }
 
 bool SigninErrorProvider::IsCanceled(NSError* error) {
   return false;
@@ skipping 13 matching lines @@
 
 NSString* SigninErrorProvider::GetSigninErrorDomain() {
   return @"signin_error_domain";
 }
 
 int SigninErrorProvider::GetCode(SigninError error) {
   return 0;
 }
 
 }  // namesace ios