Remove linked_ptr from media/.

BUG=556939

Change-Id: I66fe86602ab965622b1db26e5468f8d596c851e9
Reviewed-on: https://chromium-review.googlesource.com/c/1356867
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612827}
19 files changed