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

chrome/common/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/util/process_version.gni")
 import("//chrome/common/features.gni")
 import("//chrome/process_version_rc_template.gni")  # For branding_file_path.
 import("//extensions/features/features.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
@@ skipping 189 matching lines @@
     "//components/signin/core/common",
     "//components/strings",
     "//components/translate/content/common",
     "//components/translate/core/common",
     "//components/url_formatter",
     "//components/variations",
     "//components/version_info",
     "//components/visitedlink/common",
     "//content/public/common",
     "//crypto",
+    "//device/vr:features",
     "//extensions/common:common_constants",
     "//extensions/features",
     "//google_apis",
     "//gpu/command_buffer/service",
     "//gpu/config",
     "//ipc",
     "//media",
     "//mojo/edk/system",
     "//mojo/public/cpp/bindings",
     "//net",
@@ skipping 502 matching lines @@
 mojom("instant_mojom") {
   sources = [
     "instant.mojom",
   ]
 
   public_deps = [
     "//mojo/common:common_custom_types",
     "//url/mojo:url_mojom_gurl",
   ]
 }