Remove enable_webvr from build/config, and move it to the buildflag_header system.

build/config/features.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.
 
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # These flags are effectively global. Your feature flag should go near the
 # code it controls. Most of these items are here now because they control
@@ skipping 52 matching lines @@
   use_dbus = is_linux && !is_chromecast
 
   # Option controlling the use of GConf (the classic GNOME configuration
   # system).
   use_gconf = is_linux && !is_chromeos && !is_chromecast
 
   use_gio = is_linux && !is_chromeos && !is_chromecast
 
   # Whether or not to use external popup menu.
   use_external_popup_menu = is_android || is_mac
-
-  # Enable WebVR support by default on Android
-  # Still requires command line flag to access API
-  # TODO(bshe): Enable for other architecture too. Currently we only support arm
-  # and arm64.
-  enable_webvr = is_android && (current_cpu == "arm" || current_cpu == "arm64")
 }
 
 # Additional dependent variables -----------------------------------------------
 
 # Chrome OS: whether to also build the upcoming version of
 # ChromeVox, which can then be enabled via a command-line switch.
 enable_chromevox_next = false
 #
 # =============================================
 #   PLEASE DO NOT ADD MORE FLAGS TO THIS FILE
 # =============================================
 #
 # See comment at the top.