ui/aura: No need to not check for 'use_aura' in a aura specific build file.

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 167 matching lines @@
     "//ui/compositor:test_support",
     "//ui/events",
     "//ui/events:events_base",
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/wm",
   ]
 
   if (is_win) {
+    sources += [ "test/ui_controls_factory_aurawin.cc" ]
+
     cflags = [ "/wd4267" ]  # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   }
 
   if (use_x11) {
+    sources += [
+      "test/ui_controls_factory_aurax11.cc",
+      "test/x11_event_sender.cc",
+      "test/x11_event_sender.h",
+    ]
+
     deps += [ "//ui/gfx/x" ]
   }
-
-  if (use_aura) {
-    if (is_win) {
-      sources += [ "test/ui_controls_factory_aurawin.cc" ]
-    }
-
-    if (use_x11) {
-      sources += [
-        "test/ui_controls_factory_aurax11.cc",
-        "test/x11_event_sender.cc",
-        "test/x11_event_sender.h",
-      ]
-    }
-  }
 }
 
 executable("demo") {
   output_name = "aura_demo"
   testonly = true
 
   sources = [
     "demo/demo_main.cc",
   ]
 
@@ skipping 69 matching lines @@
     "//ui/events:gesture_detection",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 
   if (is_linux) {
     deps += [ "//third_party/mesa" ]
   }
 }