reverted:
Index: chromium-56.0.2914.3/media/BUILD.gn
===================================================================
--- chromium-56.0.2914.3.orig/media/BUILD.gn
+++ chromium-56.0.2914.3/media/BUILD.gn
@@ -25,12 +24,6 @@ buildflag_header("media_features") {
   ]
 }
 
-if (proprietary_codecs && media_use_ffmpeg) {
-  assert(
-      ffmpeg_branding != "Chromium",
-      "proprietary codecs and ffmpeg_branding set to Chromium are incompatible")
-}
-
 # Common configuration for targets in the media directory.
 # NOT for exporting.
 config("media_config") {