Complete moving video_coding headers.

Bug: webrtc:7620
Change-Id: Ic553cd083ef267b19897777340120b1f3e4765f2
Reviewed-on: https://webrtc-review.googlesource.com/39663
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Commit-Queue: Patrik Höglund <phoglund@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21633}

media/BUILD.gn

@@ -223,6 +223,7 @@ rtc_static_library("rtc_audio_video") {
   defines = []
   libs = []
   deps = [
+    "../modules/video_coding:video_codec_interface",
     "../modules/video_coding:video_coding",
     "../rtc_base:checks",
   ]

modules/video_coding/BUILD.gn

@@ -37,11 +37,6 @@ rtc_static_library("video_coding") {
     "histogram.cc",
     "histogram.h",
     "include/video_codec_initializer.h",
-
-    # TODO(bugs.webrtc.org/7620: remove these when downstream is updated).
-    "include/video_codec_interface.h",
-    "include/video_coding.h",
-    "include/video_error_codes.h",
     "inter_frame_delay.cc",
     "inter_frame_delay.h",
     "internal_defines.h",