Added accessor for the ukm service to the browser process singleton

chrome/browser/browser_process.h

 // Copyright (c) 2012 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.
 
 // This interface is for managing the global services of the application. Each
 // service is lazily created when requested the first time. The service getters
 // will return NULL if the service is not available, so callers must check for
 // this condition.
 
 #ifndef CHROME_BROWSER_BROWSER_PROCESS_H_
@@ skipping 100 matching lines @@
 }
 
 namespace rappor {
 class RapporServiceImpl;
 }
 
 namespace safe_browsing {
 class ClientSideDetectionService;
 }
 
+namespace ukm {
+class UkmService;
+}
+
 // NOT THREAD SAFE, call only from the main thread.
 // These functions shouldn't return NULL unless otherwise noted.
 class BrowserProcess {
  public:
   BrowserProcess();
   virtual ~BrowserProcess();
 
   // Called when the ResourceDispatcherHost object is created by content.
   virtual void ResourceDispatcherHostCreated() = 0;
 
   // Invoked when the user is logging out/shutting down. When logging off we may
   // not have enough time to do a normal shutdown. This method is invoked prior
   // to normal shutdown and saves any state that must be saved before we are
   // continue shutdown.
   virtual void EndSession() = 0;
 
   // Gets the manager for the various metrics-related services, constructing it
   // if necessary.
   virtual metrics_services_manager::MetricsServicesManager*
   GetMetricsServicesManager() = 0;
 
   // Services: any of these getters may return NULL
   virtual metrics::MetricsService* metrics_service() = 0;
   virtual rappor::RapporServiceImpl* rappor_service() = 0;
+  virtual ukm::UkmService* ukm_service() = 0;

[sky, 2017/01/24 22:38:01]

Can you outline why we need both GetMetricsServicesManager and this accessor,
which appears to be nothing more than a call to
GetMetricsServicesManager()->GetUkmService()?

[oystein (OOO til 10th of July), 2017/01/24 22:44:16]

I followed the example of rappor_service() and variations_service(), the main
purpose is to be able to overload it in testing_browser_process.h to return a
unit-test provided subclass of the service.

   virtual ProfileManager* profile_manager() = 0;
   virtual PrefService* local_state() = 0;
   virtual net::URLRequestContextGetter* system_request_context() = 0;
   virtual variations::VariationsService* variations_service() = 0;
 
   virtual BrowserProcessPlatformPart* platform_part() = 0;
 
   virtual extensions::EventRouterForwarder*
       extension_event_router_forwarder() = 0;
 
@@ skipping 129 matching lines @@
   // Returns the Physical Web data source.
   virtual physical_web::PhysicalWebDataSource* GetPhysicalWebDataSource() = 0;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(BrowserProcess);
 };
 
 extern BrowserProcess* g_browser_process;
 
 #endif  // CHROME_BROWSER_BROWSER_PROCESS_H_