CastAuthApk: Castkey AIDL mediaDrm plugin

Bug: 229298787
Test: Access Cast creds with MediaDrm plugin
Change-Id: I085b193ff4046d9005366c8bc8b3eb8020716b4b

cast_auth/mediadrm/CreatePluginFactories.cpp

@@ -0,0 +1,17 @@
+#include "CreatePluginFactories.h"
+
+namespace aidl {
+namespace android {
+namespace hardware {
+namespace drm {
+namespace castkey {
+
+std::shared_ptr<DrmFactory> createDrmFactory() {
+    return ::ndk::SharedRefBase::make<DrmFactory>();
+}
+
+}  // namespace castkey
+}  // namespace drm
+}  // namespace hardware
+}  // namespace android
+}  // namespace aidl