Clean up MediaMetadataRetriever use

(slightly messy cherry pick from commit 463ec6b40cf4b2e1976803f00e54619db630f1b5)

MediaMetaRetriever derives from RefBase, so we should treat it as such.

Bug: 30816425
Test: build, boot, CTS
Change-Id: I63771fb6f2864f84b722fc30290d25e5b9f36fe4
Merged-In: Ifa089636c5d997cd9e17bf23b9e5f49a7ee2cbed
1 file changed