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

services/ui/test_wm/test_wm.cc

Index: services/ui/test_wm/test_wm.cc
diff --git a/services/ui/test_wm/test_wm.cc b/services/ui/test_wm/test_wm.cc
index 58ba24aed2fe9c595d9da4223c8d193e11baef3f..e1c248a0679767187ca42d76d2ef990e24759b26 100644
--- a/services/ui/test_wm/test_wm.cc
+++ b/services/ui/test_wm/test_wm.cc
@@ -29,9 +29,9 @@
 
  private:
   // service_manager::Service:
-  void OnStart() override {
+  void OnStart(service_manager::ServiceContext* context) override {
     window_tree_client_.reset(new ui::WindowTreeClient(this, this));
-    window_tree_client_->ConnectAsWindowManager(context()->connector());
+    window_tree_client_->ConnectAsWindowManager(context->connector());
   }
 
   bool OnConnect(const service_manager::ServiceInfo& remote_info,