Take extensions out of Profile into a profile-keyed service, ExtensionSystem.

chrome/browser/profiles/profile_manager.cc

Index: chrome/browser/profiles/profile_manager.cc
diff --git a/chrome/browser/profiles/profile_manager.cc b/chrome/browser/profiles/profile_manager.cc
index 5dd29a2e2ca5fef4173c9f5719b0af70d9e9e05c..33d18a49d4fb1f7d90c1156e450d9ac68a97cb94 100644
--- a/chrome/browser/profiles/profile_manager.cc
+++ b/chrome/browser/profiles/profile_manager.cc
@@ -18,6 +18,8 @@
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/default_apps_trial.h"
 #include "chrome/browser/extensions/extension_service.h"
+#include "chrome/browser/extensions/extension_system.h"
+#include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/prefs/pref_service.h"
 #include "chrome/browser/prefs/scoped_user_pref_update.h"
 #include "chrome/browser/profiles/profile_info_cache.h"
@@ -609,9 +611,9 @@ void ProfileManager::DoFinalInit(Profile* profile, bool go_off_the_record) {
 }
 
 void ProfileManager::DoFinalInitForServices(Profile* profile,
-                                         bool go_off_the_record) {
+                                            bool go_off_the_record) {
   const CommandLine& command_line = *CommandLine::ForCurrentProcess();
-  profile->InitExtensions(!go_off_the_record);
+  ExtensionSystemFactory::GetForProfile(profile)->Init(!go_off_the_record);
   if (!command_line.HasSwitch(switches::kDisableWebResources))
     profile->InitPromoResources();
 }