Convert some GN test support targets to static libs.

services/shell/public/cpp/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_base
-source_set("cpp") {
+group("cpp") {
   public_deps = [
     ":sources",
   ]
 }
 
 # TODO(rockot): Rename this to "cpp".
-source_set("sources") {
+static_library("sources") {
   sources = [
     "application_runner.h",
     "capabilities.h",
     "connect.h",
     "connection.h",
     "connector.h",
     "identity.h",
     "interface_binder.h",
     "interface_factory.h",
     "interface_factory_impl.h",
@@ skipping 24 matching lines @@
   public_deps = [
     "//base",
     "//mojo/public/cpp/bindings",
     "//mojo/public/cpp/system",
     "//services/shell/public/interfaces",
     "//url",
   ]
 }
 
 if (!is_ios) {
-  source_set("application_support") {
+  static_library("application_support") {
     sources = [
       "lib/init_commandline.cc",
       "lib/initialize_base_and_icu.cc",
     ]
 
     deps = [
       "//base",
       "//base:i18n",
       "//mojo/public/c/system",
     ]
   }
 
-  source_set("service_test_support") {
+  static_library("service_test_support") {
     testonly = true
     sources = [
       "lib/service_test.cc",
       "service_test.h",
     ]
 
     public_deps = [
       ":cpp",
       "//testing/gtest",
     ]
 
     deps = [
       "//base",
       "//base/test:test_support",
       "//mojo/public/cpp/bindings",
       "//mojo/public/cpp/system",
       "//services/shell/background:lib",
       "//services/shell/public/interfaces:interfaces_cpp_sources",
     ]
 
     data_deps = []
   }
 }