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

mash/webtest/webtest.cc

Index: mash/webtest/webtest.cc
diff --git a/mash/webtest/webtest.cc b/mash/webtest/webtest.cc
index 6f182a80af2a3da80579ff005cef332bda0142e7..83958647191bf31189b73901c212e6e794643e81 100644
--- a/mash/webtest/webtest.cc
+++ b/mash/webtest/webtest.cc
@@ -158,12 +158,14 @@
     base::MessageLoop::current()->QuitWhenIdle();
 }
 
-void Webtest::OnStart() {
-  tracing_.Initialize(context()->connector(), context()->identity().name());
+void Webtest::OnStart(service_manager::ServiceContext* context) {
+  context_ = context;
+
+  tracing_.Initialize(context->connector(), context->identity().name());
   aura_init_ = base::MakeUnique<views::AuraInit>(
-      context()->connector(), context()->identity(), "views_mus_resources.pak");
+      context->connector(), context->identity(), "views_mus_resources.pak");
   window_manager_connection_ = views::WindowManagerConnection::Create(
-      context()->connector(), context()->identity());
+      context->connector(), context->identity());
 }
 
 bool Webtest::OnConnect(const service_manager::ServiceInfo& remote_info,
@@ -181,7 +183,7 @@
   }
 
   navigation::mojom::ViewFactoryPtr view_factory;
-  context()->connector()->ConnectToInterface("exe:navigation", &view_factory);
+  context_->connector()->ConnectToInterface("exe:navigation", &view_factory);
   navigation::mojom::ViewPtr view;
   navigation::mojom::ViewClientPtr view_client;
   navigation::mojom::ViewClientRequest view_client_request =