Improve GN header checker, make //ui pass.

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 154 matching lines @@
     "test/test_windows.h",
     "test/test_window_delegate.cc",
     "test/test_window_delegate.h",
     "test/ui_controls_factory_aura.h",
     "test/window_event_dispatcher_test_api.cc",
     "test/window_event_dispatcher_test_api.h",
     "test/window_test_api.cc",
     "test/window_test_api.h",
   ]
 
+  public_deps = [
+    ":aura",
+  ]
   deps = [
-    ":aura",
     "//skia",
     "//testing/gtest",
-    "//ui/base",
     "//ui/base:test_support",
     "//ui/compositor:test_support",
     "//ui/events",
     "//ui/events:events_base",
     "//ui/events:test_support",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/wm",
   ]
 
@@ skipping 51 matching lines @@
 
 executable("bench") {
   output_name = "aura_bench"
   testonly = true
 
   sources = [
     "bench/bench_main.cc",
   ]
 
   deps = [
-    ":aura",
     ":test_support",
     "//base",
     "//base:i18n",
     "//cc",
     "//gpu/command_buffer/client:gles2_interface",
     "//skia",
     "//third_party/icu",
     "//ui/base",
     "//ui/compositor",
     "//ui/compositor:test_support",
@@ skipping 14 matching lines @@
   output_name = "aura_unittests"
   sources = [
     "gestures/gesture_recognizer_unittest.cc",
     "test/run_all_unittests.cc",
     "window_event_dispatcher_unittest.cc",
     "window_targeter_unittest.cc",
     "window_unittest.cc",
   ]
 
   deps = [
-    ":aura",
     ":test_support",
     "//base/allocator",
     "//base/test:test_support",
     "//skia",
     "//testing/gtest",
-    "//ui/base",
     "//ui/base:test_support",
-    "//ui/compositor",
     "//ui/compositor:test_support",
-    "//ui/events",
-    "//ui/events:events_base",
+    "//ui/events:test_support",
     "//ui/events:gesture_detection",
     "//ui/gfx",
     "//ui/gfx/geometry",
     "//ui/gl",
   ]
 
   if (is_linux) {
     deps += [
       "//third_party/mesa",
     ]
   }
 }