[ios] Adds OmahaServiceProvider.

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 127 matching lines @@
     const {
   return nullptr;
 }
 
 id<LogoVendor> ChromeBrowserProvider::CreateLogoVendor(
     ios::ChromeBrowserState* browser_state,
     id<UrlLoader> loader) const {
   return nil;
 }
 
+OmahaServiceProvider* ChromeBrowserProvider::GetOmahaServiceProvider() const {
+  return nil;
+}
+
 bool ChromeBrowserProvider::ShouldEmbedderRegisterVoiceSearchPrefs() const {
   return false;
 }
 
 }  // namespace ios