Fix compilation of components_unittests with disable_file_support=true.

net/features.gni

+# Copyright 2016 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/features.gni")
+
+declare_args() {
+  # Disables support for file URLs.  File URL support requires use of icu.
+  disable_file_support = false
+
+  # WebSockets and socket stream code are not used on iOS and are optional in
+  # cronet.
+  enable_websockets = !is_ios
+  disable_ftp_support = is_ios || is_chromecast
+
+  # Enable Kerberos authentication. It is disabled by default on ChromeOS, iOS,
+  # Chromecast, at least for now. This feature needs configuration (krb5.conf
+  # and so on).
+  use_kerberos = !is_chromeos && !is_ios && !is_chromecast
+
+  # Do not disable brotli filter by default.
+  disable_brotli_filter = false
+}