Convert some GN test support targets to static libs.

ui/aura/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("//build/config/ui.gni")
 import("//testing/test.gni")
 
 component("aura") {
   sources = [
     "../wm/public/activation_change_observer.cc",
@@ skipping 132 matching lines @@
   }
 
   if (is_android) {
     deps += [
       "//ui/platform_window/android",
       "//ui/platform_window/android:platform_window_java",
     ]
   }
 }
 
-source_set("test_support") {
+static_library("test_support") {
   testonly = true
   sources = [
     "test/aura_test_base.cc",
     "test/aura_test_base.h",
     "test/aura_test_helper.cc",
     "test/aura_test_helper.h",
     "test/aura_test_utils.cc",
     "test/aura_test_utils.h",
     "test/env_test_helper.h",
     "test/event_generator_delegate_aura.cc",
@@ skipping 114 matching lines @@
   ]
 
   if (is_linux) {
     deps += [ "//third_party/mesa" ]
   }
 
   data_deps = [
     "//third_party/mesa:osmesa",
   ]
 }