Convert USE_PROPRIETARY_CODECS to a buildflag header.

media/media_options.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/chromecast_build.gni")
 import("//build/config/features.gni")
 import("//testing/libfuzzer/fuzzer_test.gni")
 
 declare_args() {
+  # Enables proprietary codecs and demuxers; e.g. H264, AAC, MP3, and MP4.
+  # We always build Google Chrome and Chromecast with proprietary codecs.
+  proprietary_codecs = is_chrome_branded || is_chromecast
+}
+
+# Must be a separate block since some of these depend on the proprietary_codecs
+# flag.
+declare_args() {
   # Allows distributions to link pulseaudio directly (DT_NEEDED) instead of
   # using dlopen. This helps with automated detection of ABI mismatches and
   # prevents silent errors.
   link_pulseaudio = false
 
   # Enable usage of FFmpeg within the media library. Used for most software
   # based decoding, demuxing, and sometimes optimized FFTs. If disabled,
   # implementors must provide their own demuxers and decoders.
   media_use_ffmpeg = true
 
@@ skipping 117 matching lines @@
     }
   }
 }
 
 declare_args() {
   # This switch defines whether the Media Remoting implementation will be built.
   # When enabled, media is allowed to be renderer and played back on remote
   # devices when the tab is being casted and other conditions are met.
   enable_media_remoting = !is_chromecast && !is_ios && !is_android
 }