Allow ChromeIdentityService in ChromeBrowserProvider to be overriden.

ios/public/provider/chrome/browser/chrome_browser_provider.mm

 // Copyright 2013 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/chrome_browser_provider.h"
 
 #include <cstddef>
 
 #include "base/logging.h"
 #include "components/metrics/metrics_provider.h"
@@ skipping 32 matching lines @@
 InfoBarViewPlaceholder ChromeBrowserProvider::CreateInfoBarView(
     CGRect frame,
     InfoBarViewDelegate* delegate) {
   return nullptr;
 }
 
 SigninResourcesProvider* ChromeBrowserProvider::GetSigninResourcesProvider() {
   return nullptr;
 }
 
+void ChromeBrowserProvider::SetChromeIdentityServiceForTesting(
+    std::unique_ptr<ChromeIdentityService> service) {}
+
 ChromeIdentityService* ChromeBrowserProvider::GetChromeIdentityService() {
   return nullptr;
 }
 
 LiveTabContextProvider* ChromeBrowserProvider::GetLiveTabContextProvider() {
   return nullptr;
 }
 
 GeolocationUpdaterProvider*
 ChromeBrowserProvider::GetGeolocationUpdaterProvider() {
@@ skipping 36 matching lines @@
   return false;
 }
 
 std::unique_ptr<browser_sync::SyncedWindowDelegatesGetter>
 ChromeBrowserProvider::CreateSyncedWindowDelegatesGetter(
     ios::ChromeBrowserState* browser_state) {
   return nullptr;
 }
 
 }  // namespace ios