Add mus_demo mojo app.

components/mus/demo/main.cc

Index: components/mus/demo/main.cc
diff --git a/mash/quick_launch/main.cc b/components/mus/demo/main.cc
similarity index 68%
copy from mash/quick_launch/main.cc
copy to components/mus/demo/main.cc
index 64ad1077f78815b57b740cee7d346e0fe45a4dd7..64d115ca656770cf136108293f9284d13ed020e3 100644
--- a/mash/quick_launch/main.cc
+++ b/components/mus/demo/main.cc
@@ -2,12 +2,12 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "mash/quick_launch/quick_launch_application.h"
+#include "components/mus/demo/mus_demo.h"
 #include "mojo/public/c/system/main.h"
 #include "mojo/shell/public/cpp/application_runner.h"
 
 MojoResult MojoMain(MojoHandle shell_handle) {
-  mojo::ApplicationRunner runner(
-      new mash::quick_launch::QuickLaunchApplication);
+  mojo::ApplicationRunner runner(new mus_demo::MusDemo);
+  runner.set_message_loop_type(base::MessageLoop::TYPE_UI);
   return runner.Run(shell_handle);
 }