Remove some global UI defines

third_party/WebKit/Source/config.gni

 # 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("//third_party/WebKit/public/public_features.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
 }
 if (current_cpu == "arm") {
   import("//build/config/arm.gni")
 }
 
 declare_args() {
   # If true, doesn't compile debug symbols into webcore reducing the
@@ skipping 44 matching lines @@
 
 if (use_webaudio_ffmpeg) {
   feature_defines_list += [ "WTF_USE_WEBAUDIO_FFMPEG=1" ]
 }
 
 if (use_openmax_dl_fft) {
   feature_defines_list += [ "WTF_USE_WEBAUDIO_OPENMAX_DL_FFT=1" ]
 }
 
 if (use_default_render_theme) {
+  # Mirrors the USE_DEFAULT_RENDER_THEME buildflag_header in WebKit/public.
+  # If/when Blink can use buildflag headers, this should be removed in
+  # preference to that.
   feature_defines_list += [ "WTF_USE_DEFAULT_RENDER_THEME=1" ]
 }
 if (blink_logging_always_on) {
   feature_defines_list += [ "LOG_DISABLED=0" ]
 }