mash: Port sysui's WallpaperDelegateMus to mojo:ash.

ash/mus/window_manager_application.cc

Index: ash/mus/window_manager_application.cc
diff --git a/ash/mus/window_manager_application.cc b/ash/mus/window_manager_application.cc
index 614722a09855dfa1c52b67590b40248fdbe1bb0c..de0f9426ee95195896eef30466914f34833ffcee 100644
--- a/ash/mus/window_manager_application.cc
+++ b/ash/mus/window_manager_application.cc
@@ -11,6 +11,7 @@
 #include "ash/mus/accelerators/accelerator_registrar_impl.h"
 #include "ash/mus/native_widget_factory_mus.h"
 #include "ash/mus/shelf_delegate_mus.h"
+#include "ash/mus/wallpaper_delegate_mus.h"
 #include "ash/mus/window_manager.h"
 #include "base/bind.h"
 #include "base/memory/ptr_util.h"
@@ -152,6 +153,7 @@ void WindowManagerApplication::OnStart(const shell::Identity& identity) {
 bool WindowManagerApplication::OnConnect(const shell::Identity& remote_identity,
                                          shell::InterfaceRegistry* registry) {
   registry->AddInterface<ash::mojom::ShelfController>(this);
+  registry->AddInterface<ash::mojom::WallpaperController>(this);
   registry->AddInterface<ui::mojom::AcceleratorRegistrar>(this);
   if (remote_identity.name() == "mojo:mash_session") {
     connector()->ConnectToInterface(remote_identity, &session_);
@@ -171,6 +173,16 @@ void WindowManagerApplication::Create(
 }
 
 void WindowManagerApplication::Create(
+    const ::shell::Identity& remote_identity,
+    ash::mojom::WallpaperControllerRequest request) {
+  ash::mojom::WallpaperController* wallpaper_controller =
+      static_cast<WallpaperDelegateMus*>(WmShell::Get()->wallpaper_delegate());
+  DCHECK(wallpaper_controller);
+  wallpaper_controller_bindings_.AddBinding(wallpaper_controller,
+                                            std::move(request));
+}
+
+void WindowManagerApplication::Create(
     const shell::Identity& remote_identity,
     ui::mojom::AcceleratorRegistrarRequest request) {
   if (!window_manager_->window_manager_client())