mojo_js_standalone will quit after the last JSApp quits

mojo/apps/js/application_delegate_impl.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 "mojo/apps/js/application_delegate_impl.h"
 
 #include "gin/array_buffer.h"
 #include "gin/public/isolate_holder.h"
 #include "mojo/apps/js/js_app.h"
 #include "mojo/public/cpp/application/application_impl.h"
@@ skipping 19 matching lines @@
   app_vector_.push_back(app);
   // TODO(hansmuller): deal with the Start() return value.
   app->Start();
 }
 
 void ApplicationDelegateImpl::QuitJSApp(JSApp* app) {
   AppVector::iterator itr =
       std::find(app_vector_.begin(), app_vector_.end(), app);
   if (itr != app_vector_.end())
     app_vector_.erase(itr);
+  if (app_vector_.empty())
+    base::MessageLoop::current()->QuitWhenIdle();
 }
 
 void ApplicationDelegateImpl::ConnectToService(
     ScopedMessagePipeHandle pipe_handle,
     const std::string& application_url,
     const std::string& interface_name) {
   CHECK(application_impl_);
   ServiceProvider* service_provider =
       application_impl_->ConnectToApplication(application_url)
           ->GetServiceProvider();
   service_provider->ConnectToService(interface_name, pipe_handle.Pass());
 }
 
 }  // namespace apps
 }  // namespace mojo