mojo_application.gni - data deps are called data_deps these days.

examples/apptest/BUILD.gn

 # Copyright 2014 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.
 
 import("//mojo/public/mojo_application.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 
 group("apptest") {
   testonly = true
 
@@ skipping 33 matching lines @@
 
   deps = [
     ":bindings",
     "//mojo/public/cpp/application:standalone",
     "//mojo/public/cpp/application:test_support_standalone",
     "//mojo/public/cpp/bindings:callback",
     "//mojo/public/cpp/environment",
     "//mojo/public/cpp/system",
   ]
 
-  datadeps = [
-    ":service",
-  ]
+  data_deps = [ ":service" ]
 }
 
 mojom("bindings") {
   sources = [
     "example_service.mojom",
   ]
 }