mash: Move directly linked NewWindowDelegate to mojom::NewWindowClient.

chrome/browser/chrome_content_browser_manifest_overlay.json

 {
   "name": "service:content_browser",
   "display_name": "Chrome",
   "interface_provider_specs": {
     "service_manager:connector": {
       "provides": {
         "renderer": [
           "autofill::mojom::AutofillDriver",
           "autofill::mojom::PasswordManagerDriver",
           "extensions::StashService",
           "metrics::mojom::LeakDetector",
           "rappor::mojom::RapporRecorder",
           "startup_metric_utils::mojom::StartupMetricHost",
           "translate::mojom::ContentTranslateDriver"
         ],
         "gpu": [
           "metrics::mojom::CallStackProfileCollector"
         ],
         "ash": [
           "ash::mojom::LocaleNotificationController",
+          "ash::mojom::NewWindowClient",
           "ash::mojom::ShelfController",
           "ash::mojom::SystemTray",
           "ash::mojom::SystemTrayClient",
           "ash::mojom::WallpaperController",
           "ash::mojom::WallpaperManager",
           "ash::mojom::VolumeController"
         ],
         "mash:launchable": [
           "mash::mojom::Launchable"
         ]
       }
     }
   }
 }