media : Convert missing mojo media defines to buildflags

Bug: none
Change-Id: I117fcb0d9936ea73ad92fb9d5e9d4f180b42817e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1974714Reviewed-by: John Rummell <jrummell@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727314}

media/mojo/services/media_service_factory.cc

@@ -7,6 +7,7 @@
 #include <memory>
 
 #include "base/logging.h"
+#include "media/mojo/buildflags.h"
 #include "media/mojo/services/gpu_mojo_media_client.h"
 #include "media/mojo/services/media_service.h"
 #include "media/mojo/services/test_mojo_media_client.h"
@@ -19,7 +20,7 @@ namespace media {
 
 std::unique_ptr<MediaService> CreateMediaService(
     mojo::PendingReceiver<mojom::MediaService> receiver) {
-#if defined(ENABLE_TEST_MOJO_MEDIA_CLIENT)
+#if BUILDFLAG(ENABLE_TEST_MOJO_MEDIA_CLIENT)
   return CreateMediaServiceForTesting(std::move(receiver));
 #elif defined(OS_ANDROID)
   return std::make_unique<MediaService>(