Moves network control interface to API.

This prepares for allowing injection of a network controller.

Bug: webrtc:9155
Change-Id: I5624f47738db9c5cd4750eac76cb6289e06a7aa3
Reviewed-on: https://webrtc-review.googlesource.com/73100
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Sebastian Jansson <srte@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23188}
diff --git a/modules/BUILD.gn b/modules/BUILD.gn
index 39a609a..0182584 100644
--- a/modules/BUILD.gn
+++ b/modules/BUILD.gn
@@ -56,6 +56,7 @@
     "../api:optional",
     "../api:video_frame_api",
     "../api:video_frame_api_i420",
+    "../api/transport:network_control",
     "../rtc_base:deprecation",
     "../rtc_base:rtc_base_approved",
     "video_coding:codec_globals_headers",