Make mojo/application:test_support a group target.

mojo/application/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.
 
 # GYP version: mojo/mojo_base.gyp:mojo_application_chromium
 source_set("application") {
   sources = [
     "application_runner_chromium.cc",
     "application_runner_chromium.h",
   ]
@@ skipping 17 matching lines @@
     ":application",
     "//base",
     "//mojo/common",
     "//mojo/environment:chromium",
     "//third_party/mojo/src/mojo/public/interfaces/application",
     "//third_party/mojo_services/src/content_handler/public/interfaces",
     "//mojo/services/network/public/interfaces",
   ]
 }
 
-source_set("test_support") {
+source_set("test_support_source_set") {
   testonly = true
   sources = [
     "application_test_base_chromium.cc",
     "application_test_base_chromium.h",
     "application_test_main_chromium.cc",
   ]
 
   deps = [
     "//base",
     "//base/test:test_support",
     "//third_party/mojo/src/mojo/public/cpp/application:application",
     "//third_party/mojo/src/mojo/public/cpp/bindings",
     "//third_party/mojo/src/mojo/public/cpp/environment",
     "//third_party/mojo/src/mojo/public/cpp/system",
     "//testing/gtest",
   ]
+}
 
-  # TODO(msw): Any apptest target should build mojo shell; see crbug.com/477104.
+# This group wraps the source_set above, so building any apptest that depends
+# on this target also builds this target's data_deps; see crbug.com/477104.
+group("test_support") {
+  testonly = true
+  public_deps = [
+    ":test_support_source_set",
+  ]
+
   data_deps = []
   if (is_android) {
     data_deps += [ "//mojo/android" ]
   }
   if (!is_component_build) {
     data_deps += [ "//mojo/shell:mojo_shell" ]
   }
 }