Add lots of testonly annotations to the GN build.

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")
 
 component("aura") {
   sources = [
     "client/aura_constants.cc",
     "client/aura_constants.h",
@@ skipping 124 matching lines @@
 
     # TODO(GYP) enable when these targets exist.
     #deps += [
     #  "//ui/events/ozone",
     #  "//ui/ozone",
     #]
   }
 }
 
 source_set("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",
     "test/event_generator_delegate_aura.h",
@@ skipping 46 matching lines @@
     if (use_x11) {
       sources += [
         "test/ui_controls_factory_aurax11.cc",
       ]
     }
   }
 }
 
 executable("demo") {
   output_name = "aura_demo"
+  testonly = true
+
   sources = [
     "demo/demo_main.cc",
   ]
 
   deps = [
     ":aura",
     ":test_support",
     "//base",
     "//base:i18n",
     "//skia",
     "//third_party/icu",
     "//ui/base",
     "//ui/compositor",
     "//ui/compositor:test_support",
     "//ui/events",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 
   if (use_x11) {
     deps += [
       "//ui/gfx/x",
     ]
   }
 }
 
 executable("bench") {
   output_name = "aura_bench"
+  testonly = true
+
   sources = [
     "bench/bench_main.cc",
   ]
 
   deps = [
     ":aura",
     ":test_support",
     "//base",
     "//base:i18n",
     "//cc",
@@ skipping 43 matching lines @@
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 
   if (is_linux) {
     deps += [
       "//third_party/mesa",
     ]
   }
 }