Removing dependency from blink/public to media/base

There is no reasonable target to depend on to get access
to media/base/video_rotation (depending on all of //media
seems to be the only way) so to clean up dependencies from
blink/public, forward declare the enum.

Better solutions are welcome.

Bug: 800764

Change-Id: Ic5079fbb11c6be189a3fc658ea9d10764c0149e5
Reviewed-on: https://chromium-review.googlesource.com/c/1301521
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Commit-Queue: Daniel Bratell <bratell@opera.com>
Cr-Commit-Position: refs/heads/master@{#603854}
2 files changed