Move enable_mdns build flag to net.

build/config/BUILD.gn

 # Copyright (c) 2013 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/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/features.gni")
@@ skipping 44 matching lines @@
 #
 # See //build/buildflag_header.gni for inntructions on generating headers.
 #
 # This will also allow you to scope your build flag to a BUILD.gn file (or a
 # .gni file if you need it from more than one place) rather than making global
 # flags. See //build/config/BUILDCONFIG.gn for advice on where to define
 # build flags.
 config("feature_flags") {
   # Don't use deprecated V8 APIs anywhere.
   defines = [ "V8_DEPRECATION_WARNINGS" ]
-  if (enable_mdns) {
-    defines += [ "ENABLE_MDNS=1" ]
-  }
   if (enable_notifications) {
     defines += [ "ENABLE_NOTIFICATIONS" ]
   }
   if (enable_plugins) {
     defines += [ "ENABLE_PLUGINS=1" ]
   }
   if (enable_pdf) {
     defines += [ "ENABLE_PDF=1" ]
   }
   if (enable_basic_printing || enable_print_preview) {
@@ skipping 386 matching lines @@
       # file doesn't exist, no error will be generated (probably MS tested this
       # case but forgot the other one?). To reproduce this error, do a build,
       # then delete the precompile.c.obj file, then build again.
       cflags_c = [ "/wd4206" ]
     } else if (is_mac) {
       precompiled_header = "build/precompile.h"
       precompiled_source = "//build/precompile.h"
     }
   }
 }