Reland of Refactor webrtc/modules/desktop_capture for GN check

.gn

 # Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/dotfile_settings.gni")
 
@@ skipping 13 matching lines @@
 check_targets = [
   "//webrtc/api/*",
   "//webrtc/audio/*",
   "//webrtc/modules/audio_coding/*",
   "//webrtc/modules/audio_conference_mixer/*",
   "//webrtc/modules/audio_device/*",
   "//webrtc/modules/audio_mixer/*",
   "//webrtc/modules/audio_processing/*",
   "//webrtc/modules/bitrate_controller/*",
   "//webrtc/modules/congestion_controller/*",
+  "//webrtc/modules/desktop_capture/*",
   "//webrtc/modules/media_file/*",
   "//webrtc/modules/pacing/*",
   "//webrtc/modules/rtp_rtcp/*",
   "//webrtc/modules/utility/*",
   "//webrtc/modules/video_capture/*",
   "//webrtc/modules/video_coding/*",
   "//webrtc/modules/video_processing/*",
   "//webrtc/modules/remote_bitrate_estimator/*",
   "//webrtc/stats:rtc_stats",
   "//webrtc/voice_engine",
   "//webrtc/voice_engine:level_indicator",
 ]
 
 # These are the list of GN files that run exec_script. This whitelist exists
 # to force additional review for new uses of exec_script, which is strongly
 # discouraged except for gypi_to_gn calls.
 exec_script_whitelist = build_dotfile_settings.exec_script_whitelist + [
                           "//third_party/boringssl/BUILD.gn",
                           "//third_party/openh264/BUILD.gn",
                           "//third_party/opus/BUILD.gn",
                           "//webrtc/modules/video_render/BUILD.gn",
                         ]