Make browser process a singleton service

chrome/browser/prefs/preferences_connection_manager.cc

 // Copyright 2016 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 "chrome/browser/prefs/preferences_connection_manager.h"
 
 #include "base/memory/ptr_util.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/prefs/preferences_service.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 79 matching lines @@
     const service_manager::Identity& remote_identity,
     prefs::mojom::PreferencesServiceFactoryRequest request) {
   factory_bindings_.AddBinding(this, std::move(request));
 }
 
 void PreferencesConnectionManager::OnStart() {
   // Certain tests have no profiles to connect to, and static initializers
   // which block the creation of test profiles.
   if (!g_browser_process->profile_manager()->GetNumberOfProfiles())
     return;
-
-  profile_shutdown_notification_ =
-      ShutdownNotifierFactory::GetInstance()
-          ->Get(ProfileManager::GetActiveUserProfile())
-          ->Subscribe(
-              base::Bind(&PreferencesConnectionManager::OnProfileDestroyed,
-                         base::Unretained(this)));
 }
 
 bool PreferencesConnectionManager::OnConnect(
     const service_manager::ServiceInfo& remote_info,
     service_manager::InterfaceRegistry* registry) {
+  if (!profile_shutdown_notification_) {
+    profile_shutdown_notification_ =
+        ShutdownNotifierFactory::GetInstance()
+            ->Get(ProfileManager::GetActiveUserProfile())
+            ->Subscribe(
+                base::Bind(&PreferencesConnectionManager::OnProfileDestroyed,
+                           base::Unretained(this)));
+  }
   registry->AddInterface<prefs::mojom::PreferencesServiceFactory>(this);
   return true;
 }