Convert USE_PROPRIETARY_CODECS to a buildflag header.

media/base/demuxer_perftest.cc

Index: media/base/demuxer_perftest.cc
diff --git a/media/base/demuxer_perftest.cc b/media/base/demuxer_perftest.cc
index 3ec8cca611bb8537024f18e61a72ec0035838f3f..6fccde25e1a2a05a77d9a23db922312aa0cbc37f 100644
--- a/media/base/demuxer_perftest.cc
+++ b/media/base/demuxer_perftest.cc
@@ -22,6 +22,7 @@
 #include "media/base/timestamp_constants.h"
 #include "media/filters/ffmpeg_demuxer.h"
 #include "media/filters/file_data_source.h"
+#include "media/media_features.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/perf/perf_test.h"
 
@@ -239,11 +240,11 @@ TEST(DemuxerPerfTest, MAYBE_Demuxer) {
   RunDemuxerBenchmark("bear-640x360.webm");
   RunDemuxerBenchmark("sfx_s16le.wav");
   RunDemuxerBenchmark("bear.flac");
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
   RunDemuxerBenchmark("bear-1280x720.mp4");
   RunDemuxerBenchmark("sfx.mp3");
 #endif
-#if defined(USE_PROPRIETARY_CODECS) && defined(OS_CHROMEOS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS) && defined(OS_CHROMEOS)
   RunDemuxerBenchmark("bear.avi");
 #endif
 }