Convert USE_PROPRIETARY_CODECS to a buildflag header.

media/cdm/aes_decryptor_unittest.cc

Index: media/cdm/aes_decryptor_unittest.cc
diff --git a/media/cdm/aes_decryptor_unittest.cc b/media/cdm/aes_decryptor_unittest.cc
index 042de6a213bd8778fbec6c14a81981d423afd666..cf9ed149337e4bedc29670cc1224a5b313fa408d 100644
--- a/media/cdm/aes_decryptor_unittest.cc
+++ b/media/cdm/aes_decryptor_unittest.cc
@@ -27,6 +27,7 @@
 #include "media/cdm/cdm_file_io.h"
 #include "media/cdm/external_clear_key_test_helper.h"
 #include "media/cdm/simple_cdm_allocator.h"
+#include "media/media_features.h"
 #include "ppapi/features/features.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest-param-test.h"
@@ -537,7 +538,7 @@ TEST_P(AesDecryptorTest, CreateSessionWithCencInitData) {
       0x00, 0x00, 0x00, 0x00  // datasize
   };
 
-#if defined(USE_PROPRIETARY_CODECS)
+#if BUILDFLAG(USE_PROPRIETARY_CODECS)
   EXPECT_CALL(cdm_client_, OnSessionMessage(NotEmpty(), _, IsJSONDictionary()));
   cdm_->CreateSessionAndGenerateRequest(
       CdmSessionType::TEMPORARY_SESSION, EmeInitDataType::CENC,