Disable sync for Lightspeed experimentation.

chrome/browser/sync/profile_sync_service_factory.cc

 // 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.
 
 #include "chrome/browser/sync/profile_sync_service_factory.h"
 
 #include "base/command_line.h"
 #include "base/memory/singleton.h"
 #include "base/prefs/pref_service.h"
 #include "chrome/browser/autofill/personal_data_manager_factory.h"
@@ skipping 14 matching lines @@
 #include "chrome/browser/sync/profile_sync_components_factory_impl.h"
 #include "chrome/browser/sync/profile_sync_service.h"
 #include "chrome/browser/sync/startup_controller.h"
 #include "chrome/browser/sync/supervised_user_signin_manager_wrapper.h"
 #include "chrome/browser/themes/theme_service_factory.h"
 #include "chrome/browser/ui/global_error/global_error_service_factory.h"
 #include "chrome/browser/webdata/web_data_service_factory.h"
 #include "components/keyed_service/content/browser_context_dependency_manager.h"
 #include "components/signin/core/browser/profile_oauth2_token_service.h"
 #include "components/signin/core/browser/signin_manager.h"
+#include "components/variations/variations_associated_data.h"
 #include "url/gurl.h"
 
 #if defined(ENABLE_EXTENSIONS)
 #include "extensions/browser/extension_system_provider.h"
 #include "extensions/browser/extensions_browser_client.h"
 #endif
 
 // static
 ProfileSyncServiceFactory* ProfileSyncServiceFactory::GetInstance() {
   return Singleton<ProfileSyncServiceFactory>::get();
 }
 
 // static
 ProfileSyncService* ProfileSyncServiceFactory::GetForProfile(
     Profile* profile) {
   if (!ProfileSyncService::IsSyncEnabled())
     return NULL;
 
+  // Disable sync experimentally to measure impact on startup time. Supervised
+  // users are unaffected, since supervised users rely completely on sync.
+  // TODO(mlerman): Remove this after the experiment. crbug.com/454788
+  if (!profile->IsSupervised() &&
+      !variations::GetVariationParamValue("LightSpeed", "DisableSync").empty())

[Nicolas Zea, 2015/02/20 18:23:26]

nit: curly braces

[Mike Lerman, 2015/02/20 18:28:50]

Done. The line wrapping's a bit ugly so I let git cl format do it.

+    return NULL;
+
   return static_cast<ProfileSyncService*>(
       GetInstance()->GetServiceForBrowserContext(profile, true));
 }
 
 ProfileSyncServiceFactory::ProfileSyncServiceFactory()
     : BrowserContextKeyedServiceFactory(
         "ProfileSyncService",
         BrowserContextDependencyManager::GetInstance()) {
   // The ProfileSyncService depends on various SyncableServices being around
   // when it is shut down.  Specify those dependencies here to build the proper
@@ skipping 75 matching lines @@
 
   pss->factory()->RegisterDataTypes(pss);
   pss->Initialize();
   return pss;
 }
 
 // static
 bool ProfileSyncServiceFactory::HasProfileSyncService(Profile* profile) {
   return GetInstance()->GetServiceForBrowserContext(profile, false) != NULL;
 }