Revert "Use mediadrm from private instead of tangorpro"

Revert submission 29489024-pixel_tablet_mediadrm

Reason for revert: DroidMonitor: Potential culprit for http://b/369192150 - Verifying through ABTD before submission. 

Reverted changes: /q/submissionid:29489024-pixel_tablet_mediadrm

Change-Id: I3c1c31b871275bf2b5ceb93120918f749f828cd1

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