Remove MediaBuffer::clone and other dead code.

Change I570374f936e434b214e9cd55e2a72f12ebeafad2 removed some dead code,
but in turn created more dead code. Remove that too.

Bug: 111407253
Test: manual, CTS
Change-Id: I4ac01935c03257857456d8e460f98f6d4f7eb430
4 files changed