Add mediadrm service

Part of media security hardening

This is an intermediate step toward moving
mediadrm to a new service separate from mediaserver.
This first step allows mediadrmservice to run based
on the system property media.mediadrmservice.enable
so it can be selectively enabled on devices that
support using native_handles for secure buffers.

bug: 22990512
Change-Id: I2208c1e87a6bd8d5bfaed06b1fdcb0509c11cff2
diff --git a/service_contexts b/service_contexts
index fe58082..39e004c 100644
--- a/service_contexts
+++ b/service_contexts
@@ -72,6 +72,7 @@
 media.resource_manager                    u:object_r:mediaserver_service:s0
 media.radio                               u:object_r:audioserver_service:s0
 media.sound_trigger_hw                    u:object_r:audioserver_service:s0
+media.drm                                 u:object_r:mediadrmserver_service:s0
 media_projection                          u:object_r:media_projection_service:s0
 media_resource_monitor                    u:object_r:media_session_service:s0
 media_router                              u:object_r:media_router_service:s0