media: Convert mojo media defines to buildflags

content/shell/renderer/shell_content_renderer_client.h

Index: content/shell/renderer/shell_content_renderer_client.h
diff --git a/content/shell/renderer/shell_content_renderer_client.h b/content/shell/renderer/shell_content_renderer_client.h
index 77b207114a511b5ef354f29eaef74a3e7321db9a..c7294ee717184f050ac64af290b18a69266c68c1 100644
--- a/content/shell/renderer/shell_content_renderer_client.h
+++ b/content/shell/renderer/shell_content_renderer_client.h
@@ -10,6 +10,7 @@
 #include "base/compiler_specific.h"
 #include "build/build_config.h"
 #include "content/public/renderer/content_renderer_client.h"
+#include "media/mojo/features.h"
 
 namespace web_cache {
 class WebCacheImpl;
@@ -34,7 +35,7 @@ class ShellContentRendererClient : public ContentRendererClient {
   void DidInitializeWorkerContextOnWorkerThread(
       v8::Local<v8::Context> context) override;
 
-#if defined(ENABLE_MOJO_CDM)
+#if BUILDFLAG(ENABLE_MOJO_CDM)
   void AddSupportedKeySystems(
       std::vector<std::unique_ptr<media::KeySystemProperties>>* key_systems)
       override;