Convert USE_PROPRIETARY_CODECS to a buildflag header.

components/cdm/renderer/external_clear_key_key_system_properties.cc

Index: components/cdm/renderer/external_clear_key_key_system_properties.cc
diff --git a/components/cdm/renderer/external_clear_key_key_system_properties.cc b/components/cdm/renderer/external_clear_key_key_system_properties.cc
index 8e59f3558f0a9895df68bc1613ec713e4697e6c5..b43b5c682a8cfaaf0eed35710e438d88c39595cb 100644
--- a/components/cdm/renderer/external_clear_key_key_system_properties.cc
+++ b/components/cdm/renderer/external_clear_key_key_system_properties.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "media/base/eme_constants.h"
+#include "media/media_features.h"
 #include "ppapi/features/features.h"
 
 namespace cdm {
@@ -32,11 +33,11 @@ bool ExternalClearKeyProperties::IsSupportedInitDataType(
       return true;
 
     case media::EmeInitDataType::CENC:
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
       return true;
 #else
       return false;
-#endif  // defined(USE_PROPRIETARY_CODECS)
+#endif  // BUILDFLAG(USE_PROPRIETARY_CODECS)
 
     case media::EmeInitDataType::UNKNOWN:
       return false;
@@ -46,7 +47,7 @@ bool ExternalClearKeyProperties::IsSupportedInitDataType(
 }
 
 media::SupportedCodecs ExternalClearKeyProperties::GetSupportedCodecs() const {
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
   return media::EME_CODEC_MP4_ALL | media::EME_CODEC_WEBM_ALL;
 #else
   return media::EME_CODEC_WEBM_ALL;