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

chrome/browser/sync/glue/app_data_type_controller.cc

Index: chrome/browser/sync/glue/app_data_type_controller.cc
diff --git a/chrome/browser/sync/glue/app_data_type_controller.cc b/chrome/browser/sync/glue/app_data_type_controller.cc
index 327ca387cfac3bf85666a4f45306fe8fe591ef59..f177ce43b410008ea1339421b409b1db1453836b 100644
--- a/chrome/browser/sync/glue/app_data_type_controller.cc
+++ b/chrome/browser/sync/glue/app_data_type_controller.cc
@@ -5,6 +5,8 @@
 #include "chrome/browser/sync/glue/app_data_type_controller.h"
 
 #include "base/metrics/histogram.h"
+#include "chrome/browser/extensions/extension_system.h"
+#include "chrome/browser/extensions/extension_system_factory.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sync/profile_sync_components_factory.h"
 
@@ -27,7 +29,7 @@ syncable::ModelType AppDataTypeController::type() const {
 }
 
 bool AppDataTypeController::StartModels() {
-  profile_->InitExtensions(true);
+  ExtensionSystemFactory::GetForProfile(profile_)->Init(true);
   return true;
 }