Convert some GN test support targets to static libs.

services/shell/background/tests/BUILD.gn

 # Copyright 2016 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")
 import("//testing/test.gni")
 
-source_set("test_support") {
+static_library("test_support") {
   sources = [
     "test_catalog_store.cc",
     "test_catalog_store.h",
   ]
 
   deps = [
     "//base",
     "//services/catalog:lib",
     "//url",
   ]
@@ skipping 34 matching lines @@
     "test_service.cc",
   ]
 
   deps = [
     ":test_app_bindings",
     "//base",
     "//services/shell/public/cpp:sources",
     "//services/shell/public/interfaces",
   ]
 }