Add rudimentary mash shelf functionality.

mash/wm/window_manager_application.cc

Index: mash/wm/window_manager_application.cc
diff --git a/mash/wm/window_manager_application.cc b/mash/wm/window_manager_application.cc
index 748bc481030b538efb942bc6f6a5ffc0c34199b9..1f57a65a6408b5091632b0b09c5a92c780f8f9b4 100644
--- a/mash/wm/window_manager_application.cc
+++ b/mash/wm/window_manager_application.cc
@@ -92,6 +92,7 @@ bool WindowManagerApplication::ConfigureIncomingConnection(
     mojo::ApplicationConnection* connection) {
   connection->AddService<mus::mojom::AcceleratorRegistrar>(this);
   connection->AddService<mus::mojom::WindowManager>(this);
+  connection->AddService<mus::mojom::UserWindowController>(this);
   return true;
 }
 
@@ -137,6 +138,11 @@ void WindowManagerApplication::OnEmbed(mus::Window* root) {
                                        std::move(*request));
   requests_.clear();
 
+  for (auto request : user_window_controller_requests_)
+    user_window_controller_binding_.AddBinding(window_manager_.get(),
+                                               std::move(*request));
+  user_window_controller_requests_.clear();
+
   shadow_controller_.reset(new ShadowController(root->connection()));
 }
 
@@ -178,6 +184,19 @@ void WindowManagerApplication::Create(
   }
 }
 
+void WindowManagerApplication::Create(
+    mojo::ApplicationConnection* connection,
+    mojo::InterfaceRequest<mus::mojom::UserWindowController> request) {
+  if (root_) {
+    user_window_controller_binding_.AddBinding(window_manager_.get(),
+                                               std::move(request));
+  } else {
+    user_window_controller_requests_.push_back(
+        new mojo::InterfaceRequest<mus::mojom::UserWindowController>(
+            std::move(request)));
+  }
+}
+
 void WindowManagerApplication::OnWindowDestroyed(mus::Window* window) {
   DCHECK_EQ(window, root_);
   root_->RemoveObserver(this);