Flush UKM metrics when backgrounded on Android and iOS.

ios/chrome/test/testing_application_context.h

 // 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.
 
 #ifndef IOS_CHROME_TEST_TESTING_APPLICATION_CONTEXT_H_
 #define IOS_CHROME_TEST_TESTING_APPLICATION_CONTEXT_H_
 
 #include <memory>
 
 #include "base/macros.h"
@@ skipping 22 matching lines @@
   void OnAppEnterForeground() override;
   void OnAppEnterBackground() override;
   bool WasLastShutdownClean() override;
   PrefService* GetLocalState() override;
   net::URLRequestContextGetter* GetSystemURLRequestContext() override;
   const std::string& GetApplicationLocale() override;
   ios::ChromeBrowserStateManager* GetChromeBrowserStateManager() override;
   metrics_services_manager::MetricsServicesManager* GetMetricsServicesManager()
       override;
   metrics::MetricsService* GetMetricsService() override;
+  ukm::UkmService* GetUkmService() override;
   variations::VariationsService* GetVariationsService() override;
   rappor::RapporServiceImpl* GetRapporServiceImpl() override;
   net_log::ChromeNetLog* GetNetLog() override;
   network_time::NetworkTimeTracker* GetNetworkTimeTracker() override;
   IOSChromeIOThread* GetIOSChromeIOThread() override;
   gcm::GCMDriver* GetGCMDriver() override;
   component_updater::ComponentUpdateService* GetComponentUpdateService()
       override;
   CRLSetFetcher* GetCRLSetFetcher() override;
   physical_web::PhysicalWebDataSource* GetPhysicalWebDataSource() override;
 
  private:
   base::ThreadChecker thread_checker_;
   std::string application_locale_;
   PrefService* local_state_;
   ios::ChromeBrowserStateManager* chrome_browser_state_manager_;
   std::unique_ptr<network_time::NetworkTimeTracker> network_time_tracker_;
   bool was_last_shutdown_clean_;
 
   DISALLOW_COPY_AND_ASSIGN(TestingApplicationContext);
 };
 
 #endif  // IOS_CHROME_TEST_TESTING_APPLICATION_CONTEXT_H_