Remove usage of ffmpeg in webrtc stack. (#191)

Co-authored-by: Johny Qiu <[email protected]>

Author: jianjunz

modules/video_coding/BUILD.gn

@@ -506,15 +506,6 @@ rtc_library("webrtc_h264") {
   ]
 
   defines = []
-  if (ffmpeg_branding == "Chrome" || ffmpeg_branding == "Chromium") {
-    sources += [
-      "codecs/h264/h264_color_space.cc",
-      "codecs/h264/h264_color_space.h",
-      "codecs/h264/h264_decoder_impl.cc",
-      "codecs/h264/h264_decoder_impl.h",
-    ]
-    defines += [ "OWT_USE_FFMPEG" ]
-  }
 
   deps = [
     ":video_codec_interface",
@@ -547,10 +538,6 @@ rtc_library("webrtc_h264") {
   if (rtc_use_h264) {
     deps += [ "//third_party/openh264:encoder" ]
 
-    if (ffmpeg_branding == "Chrome" || ffmpeg_branding == "Chromium") {
-      deps += [ "//third_party/ffmpeg" ]
-    }
-
     if (!build_with_mozilla) {
       deps += [ "../../media:rtc_media_base" ]
     }