Move midi files from //content/renderer/media to ../midi

This CL moves the midi-specific files from //content/renderer/media
into //content/renderer/media/midi, to replicate the //media/midi
infra. Moved OWNERS to it.

$ mkdir midi
$ git mv *midi_* midi
$ git mv *midiacc* midi
$ tools/git/mass-rename.py

No new code.

Bug: 739232
Change-Id: Id15614f74e960eb85faf3ca3eb8cd24e6263a83d
Reviewed-on: https://chromium-review.googlesource.com/914696
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Reviewed-by: Takashi Toyoshima <toyoshim@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#536373}
10 files changed