Convert USE_PROPRIETARY_CODECS to a buildflag header.

third_party/widevine/cdm/BUILD.gn

 # 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/chrome_build.gni")
 import("//build/config/features.gni")
 import("//chrome/process_version_rc_template.gni")
 import("//media/cdm/ppapi/cdm_paths.gni")
 import("//media/cdm/ppapi/ppapi_cdm_adapter.gni")
 import("//ppapi/features/features.gni")
@@ skipping 55 matching lines @@
   ]
 }
 
 source_set("headers") {
   public = [
     "widevine_cdm_common.h",
   ]
 
   public_deps = [
     ":version_h",  # Forward permission to use version header.
+    "//media:media_features",
     "//ppapi/features",
   ]
 }
 
 if (widevine_cdm_binary_files != []) {
   copy("widevinecdm") {
     sources = widevine_cdm_binary_files
     outputs = [
       "$root_out_dir/$widevine_cdm_path/{{source_file_part}}",
     ]
@@ skipping 98 matching lines @@
 # on the license server.
 source_set("widevine_test_license_server") {
   if (is_chrome_branded && is_linux) {
     deps = [
       # TODO(jrummell)
       # This target should be removed and targets should have data_deps on this target:
       #"//third_party/widevine/test/license_server/license_server.gyp:test_license_server"
     ]
   }
 }