[chrome.displaySource] Add WiFi Display session class skeleton and mojo service

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.
 
 # This file contains Chrome-feature-related build flags (see ui.gni for
 # UI-related ones). These should theoretically be moved to the build files of
 # the features themselves.
 #
 # However, today we have many "bad" dependencies on some of these flags from,
 # e.g. base, so they need to be global to match the GYP configuration. Also,
@@ skipping 97 matching lines @@
   } else {
     safe_browsing_mode = 1
   }
 
   # Set to true make a build that disables activation of field trial tests
   # specified in testing/variations/fieldtrial_testing_config_*.json.
   # Note: this setting is ignored if is_chrome_branded.
   fieldtrial_testing_like_official_build = is_chrome_branded
 
   use_cups = (is_desktop_linux || is_mac) && !is_chromecast && !is_headless
+
+  # Enables Wi-Fi Display functionality
+  enable_wifi_display = false
 }
 
 # Default these based on the explicit value of enable_nacl, not just
 # the default value seen inside the declare_args() context.
 if (enable_nacl_untrusted == "") {
   enable_nacl_untrusted = enable_nacl
 }
 if (enable_pnacl == "") {
   enable_pnacl = enable_nacl
 }
@@ skipping 69 matching lines @@
 
 # Option controlling the use of GConf (the classic GNOME configuration
 # system).
 use_gconf = is_linux && !is_chromeos && !is_chromecast && !is_headless
 
 # Enable WebVR support by default on Android
 # Still requires command line flag to access API
 enable_webvr = is_android
 
 use_gio = is_desktop_linux && !is_headless