Revert of Service Manager: Remove ServiceContext* arg from Service::OnStart()

services/file/file_service.cc

Index: services/file/file_service.cc
diff --git a/services/file/file_service.cc b/services/file/file_service.cc
index c469fac960480e112da7bb6f68d90c7ba3672ac5..4e844209c4fa270fd82c4fa81f3b2f1cfaf12155 100644
--- a/services/file/file_service.cc
+++ b/services/file/file_service.cc
@@ -89,9 +89,9 @@
   leveldb_service_runner_->DeleteSoon(FROM_HERE, leveldb_objects_.release());
 }
 
-void FileService::OnStart() {
+void FileService::OnStart(service_manager::ServiceContext* context) {
   file_system_objects_.reset(new FileService::FileSystemObjects(
-      GetUserDirForUserId(context()->identity().user_id())));
+      GetUserDirForUserId(context->identity().user_id())));
   leveldb_objects_.reset(
       new FileService::LevelDBServiceObjects(leveldb_service_runner_));
 }