2648046: Introduce alert notification helper .app

https://chromium-review.googlesource.com/c/chromium/src/+/2648046

BUILD.gn

@@ -619,6 +619,7 @@ source_set("electron_lib") {
       "shell/renderer/printing/print_render_frame_helper_delegate.h",
     ]
     deps += [
+      "//chrome/services/mac_notifications/public/mojom",
       "//chrome/services/printing/public/mojom",
       "//components/printing/common:mojo_interfaces",
     ]