Move enable_app_list to a buildflag.

chrome/browser/resources/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("//chrome/common/features.gni")
 import("//tools/grit/grit_rule.gni")
 
 grit("net_internals_resources") {
   source = "net_internals_resources.grd"
   use_qualified_include = true
@@ skipping 22 matching lines @@
   defines = chrome_grit_defines
   outputs = [
     "grit/password_manager_internals_resources.h",
     "password_manager_internals_resources.pak",
   ]
   output_dir = "$root_gen_dir/chrome"
 }
 
 grit("policy_resources") {
   source = "md_policy/policy_resources.grd"
+  defines = chrome_grit_defines
 
   # TODO(thestig): use_qualified_include = true
   outputs = [
     "grit/policy_resources.h",
     "grit/policy_resources_map.cc",
     "grit/policy_resources_map.h",
     "policy_resources.pak",
   ]
   output_dir = "$root_gen_dir/chrome"
 }
@@ skipping 99 matching lines @@
     source = "sync_file_system_internals_resources.grd"
     use_qualified_include = true
     defines = chrome_grit_defines
     outputs = [
       "grit/sync_file_system_internals_resources.h",
       "sync_file_system_internals_resources.pak",
     ]
     output_dir = "$root_gen_dir/chrome"
   }
 }