Initial skeletal implementation of the PrincipalService. Also, use the Login()/GetUserBlessing()

examples/echo/echo_client.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdio.h>
 
 #include "examples/echo/echo.mojom.h"
 #include "mojo/public/c/system/main.h"
 #include "mojo/public/cpp/application/application_delegate.h"
 #include "mojo/public/cpp/application/application_impl.h"
 #include "mojo/public/cpp/application/application_runner.h"
 #include "mojo/public/cpp/utility/run_loop.h"
+#include "mojo/services/vanadium/security/public/interfaces/principal.mojom.h"
 
 namespace mojo {
 namespace examples {
 
 class ResponsePrinter {
  public:
   void Run(const String& value) const {
     printf("Response: \"%s\"\n", value.get().c_str());
 
     RunLoop::current()->Quit();  // All done!
   }
 };
 
 class EchoClientDelegate : public ApplicationDelegate {
  public:
   void Initialize(ApplicationImpl* app) override {
+    // Get user login credentials
+    app->ConnectToService("mojo:go_principal_service", &login_service_);
+    login_service_->Login(Callback<void(const BlessingPtr)>());
+
     app->ConnectToService("mojo:echo_server", &echo_);
+    echo_->EchoString("hello world", ResponsePrinter());
+  }
 
-    echo_->EchoString("hello world", ResponsePrinter());
+  void Quit() override {
+    login_service_->Logout();
   }
 
  private:
   EchoPtr echo_;
+  PrincipalServicePtr login_service_;
 };
 
 }  // namespace examples
 }  // namespace mojo
 
 MojoResult MojoMain(MojoHandle application_request) {
   mojo::ApplicationRunner runner(new mojo::examples::EchoClientDelegate);
   return runner.Run(application_request);
 }