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

chrome/android/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("//android_webview/webview_repack_locales_list.gni")
 import("//build/config/android/config.gni")
 import("//build/config/android/rules.gni")
 import("//build/util/process_version.gni")
 import("//chrome/android/chrome_public_apk_tmpl.gni")
 import("//chrome/android/monochrome_android_manifest_jinja_variables.gni")
 import("//chrome/chrome_paks.gni")
 import("//chrome/common/features.gni")
 import("//chrome/process_version_rc_template.gni")  # For branding_file_path.
+import("//device/vr/features.gni")
 import("//testing/test.gni")
 import("//third_party/icu/config.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//tools/resources/generate_resource_whitelist.gni")
 import("channel.gni")
 import("java_sources.gni")
 
 manifest_package = "org.chromium.chrome"
 
 chrome_public_jinja_variables = default_chrome_public_jinja_variables +
@@ skipping 839 matching lines @@
   apk_name = "ChromeSyncShellTest"
   apk_under_test = ":chrome_sync_shell_apk"
   android_manifest = chrome_sync_shell_test_apk_manifest
   android_manifest_dep = ":chrome_sync_shell_test_apk_manifest"
   deps = [
     ":chrome_sync_shell_test_apk_java",
     "//third_party/android_support_test_runner:runner_java",
   ]
   proguard_enabled = !is_java_debug
 }