H.264 video codec support using OpenH264/FFmpeg

webrtc/modules/video_coding/BUILD.gn

Index: webrtc/modules/video_coding/BUILD.gn
diff --git a/webrtc/modules/video_coding/BUILD.gn b/webrtc/modules/video_coding/BUILD.gn
index 32ac627ed244239ff8221028e0afca736261e5c4..0fd42257a410bc3087d4f057cfddc4ab9eb88e8f 100644
--- a/webrtc/modules/video_coding/BUILD.gn
+++ b/webrtc/modules/video_coding/BUILD.gn
@@ -133,16 +133,19 @@ source_set("webrtc_h264") {
     configs -= [ "//build/config/clang:find_bad_constructs" ]
   }
 
+  defines = []
   deps = [
     "../../system_wrappers",
   ]
 
   if (use_third_party_h264) {
-    # Dependency added so that variables use_openh264 and ffmpeg_branding are
-    # recognized build arguments (avoid "Build argument has no effect" error).
-    # The variables and dependencies will be used for real as soon as
-    # https://codereview.webrtc.org/1306813009/ lands. In the meantime, the
-    # build arguments are to be used by waterfall/trybots.
+    defines += [ "WEBRTC_THIRD_PARTY_H264" ]
+    sources += [
+      "codecs/h264/h264_decoder_impl.cc",
+      "codecs/h264/h264_decoder_impl.h",
+      "codecs/h264/h264_encoder_impl.cc",
+      "codecs/h264/h264_encoder_impl.h",
+    ]
     deps += [
       "//third_party/ffmpeg:ffmpeg",
       "//third_party/openh264:encoder",