mash: Have chrome set itself as the wallpaper picker.

chrome/browser/chrome_content_browser_manifest_overlay.json

 {
   "name": "content_browser",
   "display_name": "Chrome",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "renderer": [
           "autofill::mojom::AutofillDriver",
           "autofill::mojom::PasswordManagerDriver",
           "extensions::StashService",
@@ skipping 10 matching lines @@
           // to itself.
           "ash::mojom::AcceleratorController",
           "ash::mojom::CastConfig",
           "ash::mojom::LocaleNotificationController",
           "ash::mojom::NewWindowController",
           "ash::mojom::ShelfController",
           "ash::mojom::ShutdownController",
           "ash::mojom::SystemTray",
           "ash::mojom::TouchViewManager",
           "ash::mojom::WallpaperController",
-          "ash::mojom::WallpaperManager",
           "ash::mojom::VpnList",
           "keyboard::mojom::Keyboard"
         ],
         "mash:launchable": [
           "mash::mojom::Launchable"
         ]
       },
       "requires": {
         "ash": [ "ash" ],
         "image_decoder": [ "decode" ]
@@ skipping 22 matching lines @@
           // TODO(beng): These should be moved to a separate capability.
           "mojom::OmniboxPageHandler",
           "mojom::PluginsPageHandler",
           "mojom::SiteEngagementUIHandler",
           "mojom::UsbInternalsPageHandler"
         ]
       }
     }
   }
 }