Convert USE_PROPRIETARY_CODECS to a buildflag header.

build/config/BUILD.gn

 # Copyright (c) 2013 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/allocator.gni")
 import("//build/config/chrome_build.gni")
 import("//build/config/chromecast_build.gni")
 import("//build/config/crypto.gni")
 import("//build/config/dcheck_always_on.gni")
 import("//build/config/features.gni")
@@ skipping 118 matching lines @@
   }
   if (use_external_popup_menu) {
     defines += [ "USE_EXTERNAL_POPUP_MENU=1" ]
   }
   if (!enable_nacl) {
     defines += [ "DISABLE_NACL" ]
   }
   if (enable_wayland_server) {
     defines += [ "ENABLE_WAYLAND_SERVER=1" ]
   }
-  if (proprietary_codecs) {
-    defines += [ "USE_PROPRIETARY_CODECS" ]
-  }
   if (safe_browsing_mode == 1) {
     defines += [ "FULL_SAFE_BROWSING" ]
     defines += [ "SAFE_BROWSING_CSD" ]
     defines += [ "SAFE_BROWSING_DB_LOCAL" ]
   } else if (safe_browsing_mode == 2) {
     defines += [ "SAFE_BROWSING_DB_REMOTE" ]
   }
   if (is_official_build) {
     defines += [ "OFFICIAL_BUILD" ]
   }
@@ skipping 241 matching lines @@
       #
       # TODO(sof): determine VS2015 status and retire the setting from all
       # precompiled configurations.
       cflags_c = [ "/wd4206" ]
     } else if (is_mac) {
       precompiled_header = "build/precompile.h"
       precompiled_source = "//build/precompile.h"
     }
   }
 }