Move the test template to //testing/test.gni (part 2)

components/proximity_auth/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("//testing/test.gni")
+
 source_set("proximity_auth") {
   sources = [
     "base64url.cc",
     "base64url.h",
     "bluetooth_connection.cc",
     "bluetooth_connection.h",
     "bluetooth_connection_finder.cc",
     "bluetooth_connection_finder.h",
     "bluetooth_util.cc",
     "bluetooth_util_chromeos.cc",
@@ skipping 50 matching lines @@
 # Note: This is a convenience target for ease of rapid iteration during
 # development. It is not executed on any try or build bots.
 test("proximity_auth_unittests") {
   sources = [
     "run_all_unittests.cc",
   ]
   deps = [
     ":unit_tests",
   ]
 }