Convert USE_PROPRIETARY_CODECS to a buildflag header.

media/blink/webcontentdecryptionmodulesession_impl.cc

Index: media/blink/webcontentdecryptionmodulesession_impl.cc
diff --git a/media/blink/webcontentdecryptionmodulesession_impl.cc b/media/blink/webcontentdecryptionmodulesession_impl.cc
index 2ee66b0d3c087a7542747454fc204b6c6f5deb3e..0d6e509734752b970643c8b199742c2fe0762a4e 100644
--- a/media/blink/webcontentdecryptionmodulesession_impl.cc
+++ b/media/blink/webcontentdecryptionmodulesession_impl.cc
@@ -21,13 +21,14 @@
 #include "media/blink/cdm_session_adapter.h"
 #include "media/blink/webmediaplayer_util.h"
 #include "media/cdm/json_web_key.h"
+#include "media/media_features.h"
 #include "third_party/WebKit/public/platform/WebData.h"
 #include "third_party/WebKit/public/platform/WebEncryptedMediaKeyInformation.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/platform/WebURL.h"
 #include "third_party/WebKit/public/platform/WebVector.h"
 
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
 #include "media/cdm/cenc_utils.h"
 #endif
 
@@ -124,7 +125,7 @@ bool SanitizeInitData(EmeInitDataType init_data_type,
       return true;
 
     case EmeInitDataType::CENC:
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
       sanitized_init_data->assign(init_data, init_data + init_data_length);
       if (!ValidatePsshInput(*sanitized_init_data)) {
         error_message->assign("Initialization data for CENC is incorrect.");