mash: Disable ash_sysui; begin removal.

ash/sysui/public/interfaces/wallpaper.mojom

-// Copyright 2016 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.
-
-module ash.sysui.mojom;
-
-import "skia/public/interfaces/bitmap.mojom";
-
-// These values match wallpaper::WallpaperLayout.
-enum WallpaperLayout { CENTER, CENTER_CROPPED, STRETCH, TILE, };
-
-// Used by Chrome to set the wallpaper displayed by ash_sysui.
-interface WallpaperController {
-  SetWallpaper(skia.mojom.Bitmap wallpaper, WallpaperLayout layout);
-};
-
-// Used by ash_sysui to trigger Chrome's wallpaper picker functionality.
-interface WallpaperManager {
-  Open();
-};