Make Service own ServiceContext.

services/shell/tests/shutdown/shutdown_service_app.cc

Index: services/shell/tests/shutdown/shutdown_service_app.cc
diff --git a/services/shell/tests/shutdown/shutdown_service_app.cc b/services/shell/tests/shutdown/shutdown_service_app.cc
index 6328b886a9546fe68a588e85b4d9e9816cbb337d..db4381e2d53d1a59468ea7be22aad19150961f48 100644
--- a/services/shell/tests/shutdown/shutdown_service_app.cc
+++ b/services/shell/tests/shutdown/shutdown_service_app.cc
@@ -24,8 +24,6 @@ class ShutdownServiceApp
 
  private:
   // shell::Service:
-  void OnStart(Connector* connector, const Identity& identity,
-               uint32_t id) override {}
   bool OnConnect(Connection* connection) override {
     connection->AddInterface<mojom::ShutdownTestService>(this);
     return true;