DO NOT MERGE: Lock drm plugin API calls globally, not per MediaDrm instance

Bug: 22414321

Change-Id: I062c662a440a1becccd248c3b8ddf711c51e53cc
related-to-bug: 18394494
related-to-bug: 19664283
(cherry picked from commit 2fb561a6fe9bca79c50a81e90fc4bb4eb18af0be)
2 files changed