Move ENABLE_HIDPI to new build flags system

ui/base/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/buildflag_header.gni")
 import("//build/config/compiler/compiler.gni")
 import("//build/config/sanitizers/sanitizers.gni")
 import("//build/config/ui.gni")
 import("//testing/test.gni")
+import("//ui/base/ui_features.gni")
 import("//ui/ozone/ozone.gni")
 
 if (is_android) {
   import("//build/config/android/config.gni")
   import("//build/config/android/rules.gni")
 }
 
 build_ime = !is_ios
 
 # As part of building Chrome on iOS, it is necessary to run a tool on
@@ skipping 17 matching lines @@
   deps = [
     "//base",
   ]
 
   defines = [ "UI_DATA_PACK_IMPLEMENTATION" ]
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 }
 
+buildflag_header("ui_features") {
+  header = "ui_features.h"
+  flags = [ "ENABLE_HIDPI=$enable_hidpi" ]
+}
+
 component("base") {
   output_name = "ui_base"
 
   sources = [
     "accelerators/menu_label_accelerator_util_linux.cc",
     "accelerators/menu_label_accelerator_util_linux.h",
     "accelerators/platform_accelerator.h",
     "accelerators/platform_accelerator_cocoa.h",
     "accelerators/platform_accelerator_cocoa.mm",
     "android/ui_base_jni_registrar.cc",
@@ skipping 281 matching lines @@
     # Empty implementation for all other cases.
     sources += [ "touch/touch_device.cc" ]
   }
 
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
   defines = [ "UI_BASE_IMPLEMENTATION" ]
 
   public_deps = [
+    ":ui_features",
     "//base",
     "//skia",
     "//ui/events:events_base",
     "//ui/events/platform",
     "//ui/gfx",
     "//ui/gfx/geometry",
   ]
   deps = [
     "//base:base_static",
     "//base:i18n",
@@ skipping 556 matching lines @@
   }
   if (is_mac) {
     data += [ "$root_out_dir/ui_unittests Framework.framework/" ]
 
     if (is_asan && symbol_level == 0) {
       data += [ "$root_out_dir/ui_base_unittests.dSYM/" ]
     }
   }
 }
 # TODO(GYP) Mac (ui_base_tests_bundle)