Update //media to unconditionally support mp3 and mp4

Update mime parsing, eme, and unit tests to unconditionally expect support
for MP4 and MP3. Proprietary codecs in MP4 (e.g. H264) are still guarded by
the proprietary_codecs GN flag.

Also, return "probably" for <video>.canPlayType('video/ogg; codecs="vp8"')
VP8 in Ogg has been supported for a while, we just aren't making the right
claims from the API.

Bug: 327115,746579
Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: Ib05468150a1b39a6bae25d4219f827b5b542e839
Reviewed-on: https://chromium-review.googlesource.com/745529
Commit-Queue: Chrome Cunningham <chcunningham@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#522918}
17 files changed